feat: add inital in memory dispatcher

Add a simple in memory dispatcher for scalar requests and stream request.

src/Request.Tests/.editorconfig

@@ -0,0 +1,9 @@
+
+[*.{cs,vb}]
+# disable CA1822: Mark members as static
+# -> TUnit requiring instance methods for test cases
+dotnet_diagnostic.CA1822.severity = none
+# disable CA1707: Identifiers should not contain underscores
+dotnet_diagnostic.CA1707.severity = none
+# disable IDE0060: Remove unused parameter
+dotnet_diagnostic.IDE0060.severity = none

src/Request.Tests/Geekeey.Request.Tests.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <RootNamespace>Geekeey.Request</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="TUnit" />
+    <!-- additional packages -->
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <AssemblyAttribute Include="System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverageAttribute" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Request\Geekeey.Request.csproj" />
+  </ItemGroup>
+
+</Project>

src/Request.Tests/RequestDispatcherBuilderExtensionsTests.cs

@@ -0,0 +1,140 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+namespace Geekeey.Request.Tests;
+
+internal sealed class RequestDispatcherBuilderExtensionsTests
+{
+	[Test]
+	public async Task I_can_add_a_type_and_register_the_options()
+	{
+		// Arrange
+		var services = new ServiceCollection();
+		var builder = services.AddRequestDispatcher();
+		var type = typeof(TestHandler);
+
+		// Act
+		builder.Add(type);
+
+		// Assert
+		var provider = services.BuildServiceProvider();
+		var options = provider.GetRequiredService<IOptions<RequestDispatcherOptions>>().Value;
+
+		var handlers = options.GetRequestHandlers<IScalarRequestHandler<TestRequest, string>>(provider);
+		await Assert.That(handlers).Count().IsEqualTo(1);
+		await Assert.That(handlers.First()).IsTypeOf<TestHandler>();
+	}
+
+	[Test]
+	public async Task I_can_add_a_type_with_a_lifetime_and_register_the_options_and_service()
+	{
+		// Arrange
+		var services = new ServiceCollection();
+		var builder = services.AddRequestDispatcher();
+		var type = typeof(TestHandler);
+		var lifetime = ServiceLifetime.Scoped;
+
+		// Act
+		builder.Add(type, lifetime);
+
+		// Assert
+		var serviceDescriptor = services.FirstOrDefault(sd => sd.ServiceType == type);
+		await Assert.That(serviceDescriptor).IsNotNull();
+		await Assert.That(serviceDescriptor.Lifetime).IsEqualTo(lifetime);
+		await Assert.That(serviceDescriptor.ImplementationType).IsEqualTo(type);
+
+		var provider = services.BuildServiceProvider();
+		var options = provider.GetRequiredService<IOptions<RequestDispatcherOptions>>().Value;
+		var handlers = options.GetRequestHandlers<IScalarRequestHandler<TestRequest, string>>(provider);
+
+		await Assert.That(handlers).Count().IsEqualTo(1);
+	}
+
+	[Test]
+	public async Task I_can_add_an_enumerable_of_types_and_register_the_options()
+	{
+		// Arrange
+		var services = new ServiceCollection();
+		var builder = services.AddRequestDispatcher();
+		var types = new[] { typeof(TestHandler), typeof(AnotherTestHandler) };
+
+		// Act
+		builder.Add(types);
+
+		// Assert
+		var provider = services.BuildServiceProvider();
+		var options = provider.GetRequiredService<IOptions<RequestDispatcherOptions>>().Value;
+
+		var handlers1 = options.GetRequestHandlers<IScalarRequestHandler<TestRequest, string>>(provider);
+		await Assert.That(handlers1).Count().IsEqualTo(1);
+		await Assert.That(handlers1.First()).IsTypeOf<TestHandler>();
+
+		var handlers2 = options.GetRequestHandlers<IScalarRequestHandler<AnotherTestRequest, string>>(provider);
+		await Assert.That(handlers2).Count().IsEqualTo(1);
+		await Assert.That(handlers2.First()).IsTypeOf<AnotherTestHandler>();
+	}
+
+	[Test]
+	public async Task I_can_add_an_enumerable_of_types_with_a_lifetime_and_register_the_options_and_services()
+	{
+		// Arrange
+		var services = new ServiceCollection();
+		var builder = services.AddRequestDispatcher();
+		var types = new[] { typeof(TestHandler), typeof(AnotherTestHandler) };
+		var lifetime = ServiceLifetime.Singleton;
+
+		// Act
+		builder.Add(types, lifetime);
+
+		// Assert
+		foreach (var type in types)
+		{
+			var serviceDescriptor = services.FirstOrDefault(sd => sd.ServiceType == type);
+			await Assert.That(serviceDescriptor).IsNotNull();
+			await Assert.That(serviceDescriptor.Lifetime).IsEqualTo(lifetime);
+		}
+
+		var provider = services.BuildServiceProvider();
+		var options = provider.GetRequiredService<IOptions<RequestDispatcherOptions>>().Value;
+
+		await Assert.That(options.GetRequestHandlers<IScalarRequestHandler<TestRequest, string>>(provider)).Count().IsEqualTo(1);
+		await Assert.That(options.GetRequestHandlers<IScalarRequestHandler<AnotherTestRequest, string>>(provider)).Count().IsEqualTo(1);
+	}
+
+	[Test]
+	public async Task I_can_see_it_throw_when_the_builder_is_null()
+	{
+		IRequestDispatcherBuilder builder = null!;
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(() => builder.Add(typeof(TestHandler))).Throws<ArgumentNullException>();
+			await Assert.That(() => builder.Add(typeof(TestHandler), ServiceLifetime.Transient)).Throws<ArgumentNullException>();
+			await Assert.That(() => builder.Add([typeof(TestHandler)])).Throws<ArgumentNullException>();
+			await Assert.That(() => builder.Add([typeof(TestHandler)], ServiceLifetime.Transient)).Throws<ArgumentNullException>();
+		}
+	}
+
+	private sealed class TestRequest : IScalarRequest<string>;
+
+	private sealed class TestHandler : IScalarRequestHandler<TestRequest, string>
+	{
+		public Task<string> HandleAsync(TestRequest request, CancellationToken ct)
+		{
+			return Task.FromResult("ok");
+		}
+	}
+
+	private sealed class AnotherTestRequest : IScalarRequest<string>;
+
+	private sealed class AnotherTestHandler : IScalarRequestHandler<AnotherTestRequest, string>
+	{
+		public Task<string> HandleAsync(AnotherTestRequest request, CancellationToken ct)
+		{
+			return Task.FromResult("ok");
+		}
+	}
+}

src/Request.Tests/ScalarBehaviourTests.cs

@@ -0,0 +1,206 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request.Tests;
+
+internal sealed class ScalarBehaviourTests
+{
+	[Test]
+	public async Task I_can_execute_the_closed_behaviour()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<ScalarTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ScalarTestHandler))
+			.Add(typeof(ScalarTestBehavior)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<ScalarTestTracker>();
+
+		var request = new ScalarTestRequest { Value = "Hello" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Hello-Handled");
+		await Assert.That(tracker.Executed).IsTrue();
+	}
+
+	[Test]
+	public async Task I_can_execute_the_open_behaviour()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<ScalarTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ScalarTestHandler))
+			.Add(typeof(ScalarOpenBehavior<,>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<ScalarTestTracker>();
+
+		var request = new ScalarTestRequest { Value = "Hello" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Hello-Handled");
+		await Assert.That(tracker.Executed).IsTrue();
+	}
+
+	[Test]
+	public async Task I_can_chain_the_behaviours_in_order()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<ScalarTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ScalarTestHandler))
+			.Add(typeof(ScalarChainedBehaviour1))
+			.Add(typeof(ScalarChainedBehaviour2)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<ScalarTestTracker>();
+
+		var request = new ScalarTestRequest { Value = "Hello" };
+		await dispatcher.DispatchAsync(request);
+
+		// They are discovered in the order they appear in the assembly.
+		// In this file: ChainedBehaviour1, ChainedBehaviour2
+		await Assert.That(tracker.Log).Count().IsEqualTo(2);
+		await Assert.That(tracker.Log[0]).IsEquivalentTo("Behaviour1");
+		await Assert.That(tracker.Log[1]).IsEquivalentTo("Behaviour2");
+	}
+
+	[Test]
+	public async Task I_can_work_with_a_generic_wrapper_request_and_the_open_behaviour()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<ScalarTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ScalarTestWrapperHandler<>))
+			.Add(typeof(ScalarWrapperBehavior<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<ScalarTestTracker>();
+
+		var request = new ScalarTestWrapperRequest<int> { Item = 42 };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Handled-42");
+		await Assert.That(tracker.Executed).IsTrue();
+	}
+
+	[Test]
+	public async Task I_can_maintain_the_ordering_between_open_and_closed_behaviours()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<ScalarTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ScalarTestHandler))
+			.Add(typeof(ScalarOrderingOpenBehavior<,>))
+			.Add(typeof(ScalarOrderingClosedBehavior)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<ScalarTestTracker>();
+
+		var request = new ScalarTestRequest { Value = "Order" };
+		await dispatcher.DispatchAsync(request);
+
+		await Assert.That(tracker.Log).Contains("OrderingOpen");
+		await Assert.That(tracker.Log).Contains("OrderingClosed");
+	}
+}
+
+public class ScalarTestTracker
+{
+	public List<string> Log { get; } = [];
+	public bool Executed { get; set; }
+}
+
+public class ScalarOrderingOpenBehavior<TRequest, TOutput>(ScalarTestTracker tracker) : IScalarRequestBehavior<TRequest, TOutput>
+	where TRequest : IScalarRequest<TOutput>
+{
+	public Task<TOutput> HandleAsync(TRequest request, ScalarHandlerDelegate<TOutput> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("OrderingOpen");
+		return next(request, cancellationToken);
+	}
+}
+
+public class ScalarOrderingClosedBehavior(ScalarTestTracker tracker) : IScalarRequestBehavior<ScalarTestRequest, string>
+{
+	public Task<string> HandleAsync(ScalarTestRequest request, ScalarHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("OrderingClosed");
+		return next(request, cancellationToken);
+	}
+}
+
+public class ScalarTestRequest : IScalarRequest<string>
+{
+	public string Value { get; set; } = string.Empty;
+}
+
+public class ScalarTestHandler : IScalarRequestHandler<ScalarTestRequest, string>
+{
+	public Task<string> HandleAsync(ScalarTestRequest request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"{request.Value}-Handled");
+	}
+}
+
+public class ScalarTestBehavior(ScalarTestTracker tracker) : IScalarRequestBehavior<ScalarTestRequest, string>
+{
+	public async Task<string> HandleAsync(ScalarTestRequest request, ScalarHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Executed = true;
+		return await next(request, cancellationToken);
+	}
+}
+
+public class ScalarOpenBehavior<TRequest, TResponse>(ScalarTestTracker tracker) : IScalarRequestBehavior<TRequest, TResponse>
+	where TRequest : IScalarRequest<TResponse>
+{
+	public async Task<TResponse> HandleAsync(TRequest request, ScalarHandlerDelegate<TResponse> next, CancellationToken cancellationToken)
+	{
+		tracker.Executed = true;
+		return await next(request, cancellationToken);
+	}
+}
+
+public class ScalarChainedBehaviour1(ScalarTestTracker tracker) : IScalarRequestBehavior<ScalarTestRequest, string>
+{
+	public async Task<string> HandleAsync(ScalarTestRequest request, ScalarHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("Behaviour1");
+		return await next(request, cancellationToken);
+	}
+}
+
+public class ScalarChainedBehaviour2(ScalarTestTracker tracker) : IScalarRequestBehavior<ScalarTestRequest, string>
+{
+	public async Task<string> HandleAsync(ScalarTestRequest request, ScalarHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("Behaviour2");
+		return await next(request, cancellationToken);
+	}
+}
+
+public class ScalarTestWrapperRequest<T> : IScalarRequest<string>
+{
+	public T Item { get; set; } = default!;
+}
+
+public class ScalarTestWrapperHandler<T> : IScalarRequestHandler<ScalarTestWrapperRequest<T>, string>
+{
+	public Task<string> HandleAsync(ScalarTestWrapperRequest<T> request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"Handled-{request.Item}");
+	}
+}
+
+public class ScalarWrapperBehavior<T>(ScalarTestTracker tracker) : IScalarRequestBehavior<ScalarTestWrapperRequest<T>, string>
+{
+	public async Task<string> HandleAsync(ScalarTestWrapperRequest<T> request, ScalarHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Executed = true;
+		return await next(request, cancellationToken);
+	}
+}

src/Request.Tests/ScalarDispatcherTests.cs

@@ -0,0 +1,415 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+namespace Geekeey.Request.Tests;
+
+internal sealed class ScalarDispatcherTests
+{
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_open_generic_handler()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new OpenScalarRequest { Data = "Hello" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Hello-Handled");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_open_generic_handler_that_has_constraints()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ConstrainedScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new ConstrainedScalarRequest { Value = 123 };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("123-Constrained");
+	}
+
+	[Test]
+	public async Task I_can_see_it_fail_if_no_handler_is_found_even_with_an_open_generic_available()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new UnhandledScalarRequest();
+		await Assert.ThrowsAsync<InvalidOperationException>(async () => await dispatcher.DispatchAsync(request));
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_inherited_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		// InheritedScalarRequest : OpenScalarRequest.
+		// There is no Handler<InheritedScalarRequest> but there is OpenScalarHandler<TRequest> where TRequest : OpenScalarRequest.
+		// It should be able to handle InheritedScalarRequest.
+		var request = new InheritedScalarRequest { Data = "Sub" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Sub-Handled");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_inherited_handler()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(DerivedScalarHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new DerivedScalarRequest { Value = 42 };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Derived: 42");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_interface_inherited_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(InterfaceInheritedScalarHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new InterfaceInheritedScalarRequest { Name = "InterfaceTest" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("InterfaceTest-InterfaceHandled");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_deep_inheritance_in_the_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new DeepDerivedScalarRequest { Data = "Deep", DeepValue = 99 };
+		var result = await dispatcher.DispatchAsync(request);
+
+		// OpenScalarHandler<TRequest> where TRequest : OpenScalarRequest should handle this
+		await Assert.That(result).IsEquivalentTo("Deep-Handled");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_interface_constrained_handler()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(InterfaceInheritedScalarHandler))
+			.Add(typeof(InterfaceConstrainedScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new InterfaceInheritedScalarRequest { Name = "Constrained" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		// Both InterfaceInheritedScalarHandler and InterfaceConstrainedScalarHandler could match.
+		// InterfaceInheritedScalarHandler is a concrete match for InterfaceInheritedScalarRequest.
+		// InterfaceConstrainedScalarHandler is an open generic match.
+		// Currently Dispatcher.SendAsync checks concrete handlers first.
+		await Assert.That(result).IsEquivalentTo("Constrained-InterfaceHandled");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_interface_only_match()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(InterfaceConstrainedScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new AnotherNamedScalarRequest { Name = "InterfaceOnly" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		// No concrete handler for AnotherNamedScalarRequest, but InterfaceConstrainedScalarHandler<T> where T : INamedScalarRequest matches.
+		await Assert.That(result).IsEquivalentTo("InterfaceOnly-ConstrainedByInterface");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_a_nested_generic_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(WrapperScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new WrapperScalarRequest<int> { Item = 42 };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Handled-42");
+	}
+
+	[Test]
+	public async Task I_can_handle_multiple_interface_implementations()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(MultiInterfaceScalarHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new MultiInterfaceScalarRequest();
+		var result1 = await dispatcher.DispatchAsync<int>(request);
+		var result2 = await dispatcher.DispatchAsync<string>(request);
+
+		await Assert.That(result1).IsEqualTo(1);
+		await Assert.That(result2).IsEquivalentTo("One");
+	}
+
+	[Test]
+	public async Task I_can_see_it_fail_if_there_are_ambiguous_handle_methods()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(AmbiguousScalarHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new AmbiguousScalarRequest();
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Interface-Handled");
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_a_generic_interface_explicit_implementation()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ExplicitGenericScalarHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new ExplicitGenericScalarRequest { Value = "Explicit" };
+		var result = await dispatcher.DispatchAsync(request);
+
+		await Assert.That(result).IsEquivalentTo("Explicit-ExplicitHandled");
+	}
+
+	[Test]
+	public async Task I_can_see_it_throw_the_original_exception()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(FailingScalarHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new FailingScalarRequest();
+		var ex = await Assert.That(async () => await dispatcher.DispatchAsync(request)).Throws<InvalidOperationException>();
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(ex?.Message).IsEquivalentTo("Handler failed");
+			// Assert that the stack trace contains the handler's method name,
+			// which proves the exception was rethrown while preserving its origin.
+			await Assert.That(ex?.StackTrace).Contains(nameof(FailingScalarHandler.HandleAsync));
+		}
+	}
+
+	[Test]
+	public async Task I_can_see_it_throw_if_dispatcher_options_are_modified_after_build()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(FailingScalarHandler)));
+		var provider = sc.BuildServiceProvider();
+		var options = provider.GetRequiredService<IOptions<RequestDispatcherOptions>>().Value;
+		options.GetRequestBehaviors<IScalarRequestHandler<FailingScalarRequest, string>>(default!);
+
+		await Assert.That(() => options.Inspect([])).Throws<InvalidOperationException>();
+	}
+}
+
+public class FailingScalarRequest : IScalarRequest<string>
+{
+}
+
+public class FailingScalarHandler : IScalarRequestHandler<FailingScalarRequest, string>
+{
+	public Task<string> HandleAsync(FailingScalarRequest request, CancellationToken cancellationToken)
+	{
+		throw new InvalidOperationException("Handler failed");
+	}
+}
+
+public class ExplicitGenericScalarRequest : IScalarRequest<string>
+{
+	public string Value { get; set; } = string.Empty;
+}
+
+public class ExplicitGenericScalarHandler<T> : IScalarRequestHandler<ExplicitGenericScalarRequest, string>
+{
+	Task<string> IScalarRequestHandler<ExplicitGenericScalarRequest, string>.HandleAsync(ExplicitGenericScalarRequest request, CancellationToken ct)
+	{
+		return Task.FromResult($"{request.Value}-ExplicitHandled");
+	}
+}
+
+public class AmbiguousScalarRequest : IScalarRequest<string>
+{
+}
+
+public class AmbiguousScalarHandler : IScalarRequestHandler<AmbiguousScalarRequest, string>
+{
+	// Public method with the same name and signature
+	public Task<string> HandleAsync(AmbiguousScalarRequest request, CancellationToken ct)
+	{
+		return Task.FromResult("Public-Handled");
+	}
+
+	// Explicit interface implementation
+	Task<string> IScalarRequestHandler<AmbiguousScalarRequest, string>.HandleAsync(AmbiguousScalarRequest request, CancellationToken ct)
+	{
+		return Task.FromResult("Interface-Handled");
+	}
+}
+
+public class OpenScalarRequest : IScalarRequest<string>
+{
+	public string Data { get; set; } = string.Empty;
+}
+
+public class InheritedScalarRequest : OpenScalarRequest
+{
+}
+
+public class DeepDerivedScalarRequest : InheritedScalarRequest
+{
+	public int DeepValue { get; set; }
+}
+
+public class OpenScalarHandler<TRequest> : IScalarRequestHandler<TRequest, string>
+	where TRequest : OpenScalarRequest
+{
+	public Task<string> HandleAsync(TRequest request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"{request.Data}-Handled");
+	}
+}
+
+public class ConstrainedScalarRequest : IScalarRequest<string>
+{
+	public int Value { get; set; }
+}
+
+public class ConstrainedScalarHandler<TRequest> : IScalarRequestHandler<TRequest, string>
+	where TRequest : ConstrainedScalarRequest
+{
+	public Task<string> HandleAsync(TRequest request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"{request.Value}-Constrained");
+	}
+}
+
+public class UnhandledScalarRequest : IScalarRequest<string>
+{
+}
+
+public class DerivedScalarRequest : IScalarRequest<string>
+{
+	public int Value { get; set; }
+}
+
+public abstract class BaseScalarHandler<TRequest> : IScalarRequestHandler<TRequest, string>
+	where TRequest : IScalarRequest<string>
+{
+	public abstract Task<string> HandleAsync(TRequest request, CancellationToken cancellationToken);
+}
+
+public class DerivedScalarHandler : BaseScalarHandler<DerivedScalarRequest>
+{
+	public override Task<string> HandleAsync(DerivedScalarRequest request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"Derived: {request.Value}");
+	}
+}
+
+public interface INamedScalarRequest : IScalarRequest<string>
+{
+	string Name { get; }
+}
+
+public class InterfaceInheritedScalarRequest : INamedScalarRequest
+{
+	public string Name { get; set; } = string.Empty;
+}
+
+public class AnotherNamedScalarRequest : INamedScalarRequest
+{
+	public string Name { get; set; } = string.Empty;
+}
+
+public class InterfaceInheritedScalarHandler : IScalarRequestHandler<InterfaceInheritedScalarRequest, string>
+{
+	public Task<string> HandleAsync(InterfaceInheritedScalarRequest request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"{request.Name}-InterfaceHandled");
+	}
+}
+
+public class InterfaceConstrainedScalarHandler<TRequest> : IScalarRequestHandler<TRequest, string>
+	where TRequest : INamedScalarRequest
+{
+	public Task<string> HandleAsync(TRequest request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"{request.Name}-ConstrainedByInterface");
+	}
+}
+
+public class WrapperScalarRequest<T> : IScalarRequest<string>
+{
+	public T Item { get; set; } = default!;
+}
+
+public class WrapperScalarHandler<T> : IScalarRequestHandler<WrapperScalarRequest<T>, string>
+{
+	public Task<string> HandleAsync(WrapperScalarRequest<T> request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult($"Handled-{request.Item}");
+	}
+}
+
+public class MultiInterfaceScalarRequest : IScalarRequest<int>, IScalarRequest<string>
+{
+}
+
+public class MultiInterfaceScalarHandler : IScalarRequestHandler<MultiInterfaceScalarRequest, int>, IScalarRequestHandler<MultiInterfaceScalarRequest, string>
+{
+	public Task<int> HandleAsync(MultiInterfaceScalarRequest request, CancellationToken cancellationToken)
+	{
+		return Task.FromResult(1);
+	}
+
+	Task<string> IScalarRequestHandler<MultiInterfaceScalarRequest, string>.HandleAsync(MultiInterfaceScalarRequest request, CancellationToken ct)
+	{
+		return Task.FromResult("One");
+	}
+}

src/Request.Tests/StreamBehaviourTests.cs

@@ -0,0 +1,207 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request.Tests;
+
+internal sealed class StreamBehaviourTests
+{
+	[Test]
+	public async Task I_can_execute_the_closed_behaviour()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<StreamTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(StreamTestHandler))
+			.Add(typeof(StreamTestBehavior)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<StreamTestTracker>();
+
+		var request = new StreamTestRequest { Value = "Hello" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Hello-Handled-0", "Hello-Handled-1"]);
+		await Assert.That(tracker.Executed).IsTrue();
+	}
+
+	[Test]
+	public async Task I_can_execute_the_open_behaviour()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<StreamTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(StreamTestHandler))
+			.Add(typeof(StreamOpenBehavior<,>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<StreamTestTracker>();
+
+		var request = new StreamTestRequest { Value = "Hello" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Hello-Handled-0", "Hello-Handled-1"]);
+		await Assert.That(tracker.Executed).IsTrue();
+	}
+
+	[Test]
+	public async Task I_can_chain_the_behaviours_in_order()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<StreamTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(StreamTestHandler))
+			.Add(typeof(StreamChainedBehaviour1))
+			.Add(typeof(StreamChainedBehaviour2)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<StreamTestTracker>();
+
+		var request = new StreamTestRequest { Value = "Hello" };
+		await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(tracker.Log).Count().IsEqualTo(2);
+		await Assert.That(tracker.Log[0]).IsEquivalentTo("Behaviour1");
+		await Assert.That(tracker.Log[1]).IsEquivalentTo("Behaviour2");
+	}
+
+	[Test]
+	public async Task I_can_work_with_a_generic_wrapper_request_and_the_open_behaviour()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<StreamTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(StreamTestWrapperHandler<>))
+			.Add(typeof(StreamWrapperBehavior<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<StreamTestTracker>();
+
+		var request = new StreamTestWrapperRequest<int> { Item = 42 };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Handled-42-0", "Handled-42-1"]);
+		await Assert.That(tracker.Executed).IsTrue();
+	}
+
+	[Test]
+	public async Task I_can_maintain_the_ordering_between_open_and_closed_behaviours()
+	{
+		var sc = new ServiceCollection();
+		sc.AddSingleton<StreamTestTracker>();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(StreamTestHandler))
+			.Add(typeof(StreamOrderingOpenBehavior<,>))
+			.Add(typeof(StreamOrderingClosedBehavior)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+		var tracker = provider.GetRequiredService<StreamTestTracker>();
+
+		var request = new StreamTestRequest { Value = "Order" };
+		await dispatcher.DispatchAsync(request).ToListAsync();
+
+		var log = tracker.Log.ToList();
+		await Assert.That(log).Contains("Open");
+		await Assert.That(log).Contains("Closed");
+	}
+}
+
+public class StreamTestTracker
+{
+	public List<string> Log { get; } = [];
+	public bool Executed { get; set; }
+}
+
+public class StreamOrderingOpenBehavior<TRequest, TOutput>(StreamTestTracker tracker) : IStreamRequestBehavior<TRequest, TOutput>
+	where TRequest : IStreamRequest<TOutput>
+{
+	public IAsyncEnumerable<TOutput> HandleAsync(TRequest request, StreamHandlerDelegate<TOutput> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("Open");
+		return next(request, cancellationToken);
+	}
+}
+
+public class StreamOrderingClosedBehavior(StreamTestTracker tracker) : IStreamRequestBehavior<StreamTestRequest, string>
+{
+	public IAsyncEnumerable<string> HandleAsync(StreamTestRequest request, StreamHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("Closed");
+		return next(request, cancellationToken);
+	}
+}
+
+public class StreamTestRequest : IStreamRequest<string>
+{
+	public string Value { get; set; } = string.Empty;
+}
+
+public class StreamTestHandler : IStreamRequestHandler<StreamTestRequest, string>
+{
+	public async IAsyncEnumerable<string> HandleAsync(StreamTestRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"{request.Value}-Handled-0";
+		yield return $"{request.Value}-Handled-1";
+	}
+}
+
+public class StreamTestBehavior(StreamTestTracker tracker) : IStreamRequestBehavior<StreamTestRequest, string>
+{
+	public IAsyncEnumerable<string> HandleAsync(StreamTestRequest request, StreamHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Executed = true;
+		return next(request, cancellationToken);
+	}
+}
+
+public class StreamOpenBehavior<TRequest, TResponse>(StreamTestTracker tracker) : IStreamRequestBehavior<TRequest, TResponse>
+	where TRequest : IStreamRequest<TResponse>
+{
+	public IAsyncEnumerable<TResponse> HandleAsync(TRequest request, StreamHandlerDelegate<TResponse> next, CancellationToken cancellationToken)
+	{
+		tracker.Executed = true;
+		return next(request, cancellationToken);
+	}
+}
+
+public class StreamChainedBehaviour1(StreamTestTracker tracker) : IStreamRequestBehavior<StreamTestRequest, string>
+{
+	public IAsyncEnumerable<string> HandleAsync(StreamTestRequest request, StreamHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("Behaviour1");
+		return next(request, cancellationToken);
+	}
+}
+
+public class StreamChainedBehaviour2(StreamTestTracker tracker) : IStreamRequestBehavior<StreamTestRequest, string>
+{
+	public IAsyncEnumerable<string> HandleAsync(StreamTestRequest request, StreamHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Log.Add("Behaviour2");
+		return next(request, cancellationToken);
+	}
+}
+
+public class StreamTestWrapperRequest<T> : IStreamRequest<string>
+{
+	public T? Item { get; set; }
+}
+
+public class StreamTestWrapperHandler<T> : IStreamRequestHandler<StreamTestWrapperRequest<T>, string>
+{
+	public async IAsyncEnumerable<string> HandleAsync(StreamTestWrapperRequest<T> request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"Handled-{request.Item}-0";
+		yield return $"Handled-{request.Item}-1";
+	}
+}
+
+public class StreamWrapperBehavior<T>(StreamTestTracker tracker) : IStreamRequestBehavior<StreamTestWrapperRequest<T>, string>
+{
+	public IAsyncEnumerable<string> HandleAsync(StreamTestWrapperRequest<T> request, StreamHandlerDelegate<string> next, CancellationToken cancellationToken)
+	{
+		tracker.Executed = true;
+		return next(request, cancellationToken);
+	}
+}

src/Request.Tests/StreamDispatcherTests.cs

@@ -0,0 +1,418 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request.Tests;
+
+public class StreamDispatcherTests
+{
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_open_generic_handler()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new OpenStreamRequest { Data = "Hello" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Hello-Stream-0", "Hello-Stream-1"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_open_generic_handler_that_has_constraints()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ConstrainedStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new ConstrainedStreamRequest { Value = 123 };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["123-Constrained-0", "123-Constrained-1"]);
+	}
+
+	[Test]
+	public async Task I_can_see_it_fail_if_no_handler_is_found_even_with_an_open_generic_available()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new UnhandledStreamRequest();
+		await Assert.ThrowsAsync<InvalidOperationException>(async () => await dispatcher.DispatchAsync(request).FirstOrDefaultAsync().AsTask());
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_inherited_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new InheritedStreamRequest { Data = "Sub" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Sub-Stream-0", "Sub-Stream-1"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_inherited_handler()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(DerivedStreamHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new DerivedStreamRequest { Value = 42 };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Derived: 42-0", "Derived: 42-1"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_interface_inherited_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(InterfaceInheritedStreamHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new InterfaceInheritedStreamRequest { Name = "InterfaceTest" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["InterfaceTest-InterfaceHandled-0", "InterfaceTest-InterfaceHandled-1"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_deep_inheritance_in_the_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(OpenStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new DeepDerivedStreamRequest { Data = "Deep", DeepValue = 99 };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Deep-Stream-0", "Deep-Stream-1"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_interface_constrained_handler()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(InterfaceInheritedStreamHandler))
+			.Add(typeof(InterfaceConstrainedStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new InterfaceInheritedStreamRequest { Name = "Constrained" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		// Both InterfaceInheritedStreamHandler and InterfaceConstrainedStreamHandler could match.
+		// InterfaceInheritedStreamHandler is a concrete match for InterfaceInheritedStreamRequest.
+		// InterfaceConstrainedStreamHandler is an open generic match.
+		// Currently Dispatcher checks concrete handlers first.
+		await Assert.That(results).IsEquivalentTo(["Constrained-InterfaceHandled-0", "Constrained-InterfaceHandled-1"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_an_interface_only_match()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(InterfaceConstrainedStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new AnotherNamedStreamRequest { Name = "InterfaceOnly" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["InterfaceOnly-ConstrainedByInterface-0", "InterfaceOnly-ConstrainedByInterface-1"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_a_nested_generic_request()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(WrapperStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new WrapperStreamRequest<int> { Item = 42 };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Handled-42-0", "Handled-42-1"]);
+	}
+
+	[Test]
+	public async Task I_can_handle_multiple_interface_implementations()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(MultiInterfaceStreamHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new MultiInterfaceStreamRequest();
+
+		var results1 = await dispatcher.DispatchAsync<int>(request).ToListAsync();
+		var results2 = await dispatcher.DispatchAsync<string>(request).ToListAsync();
+
+		await Assert.That(results1).IsEquivalentTo([1, 2]);
+		await Assert.That(results2).IsEquivalentTo(["One", "Two"]);
+	}
+
+	[Test]
+	public async Task I_can_see_it_fail_if_there_are_ambiguous_handle_methods()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(AmbiguousStreamHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new AmbiguousStreamRequest();
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Interface-Handled"]);
+	}
+
+	[Test]
+	public async Task I_can_dispatch_a_request_async_with_a_generic_interface_explicit_implementation()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(ExplicitGenericStreamHandler<>)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new ExplicitGenericStreamRequest { Value = "Explicit" };
+		var results = await dispatcher.DispatchAsync(request).ToListAsync();
+
+		await Assert.That(results).IsEquivalentTo(["Explicit-ExplicitHandled"]);
+	}
+
+	[Test]
+	public async Task I_can_see_it_throw_the_original_exception()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(FailingStreamHandler)));
+		var provider = sc.BuildServiceProvider();
+		var dispatcher = provider.GetRequiredService<IRequestDispatcher>();
+
+		var request = new FailingStreamRequest();
+		var enumerable = dispatcher.DispatchAsync(request);
+		var ex = await Assert.ThrowsAsync<InvalidOperationException>(async () => await enumerable.ToListAsync().AsTask());
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(ex?.Message).IsEquivalentTo("Handler failed");
+			await Assert.That(ex?.StackTrace).Contains(nameof(FailingStreamHandler.HandleAsync));
+		}
+	}
+
+	[Test]
+	public async Task I_can_see_it_throw_if_dispatcher_options_are_modified_after_build()
+	{
+		var sc = new ServiceCollection();
+		sc.AddRequestDispatcher(builder => builder
+			.Add(typeof(FailingStreamHandler)));
+		var provider = sc.BuildServiceProvider();
+		var options = provider.GetRequiredService<Microsoft.Extensions.Options.IOptions<RequestDispatcherOptions>>().Value;
+		options.GetRequestHandlers<IStreamRequestHandler<FailingStreamRequest, string>>(default!);
+
+		await Assert.That(() => options.Inspect([])).Throws<InvalidOperationException>();
+	}
+}
+
+public class FailingStreamRequest : IStreamRequest<string>
+{
+}
+
+public class FailingStreamHandler : IStreamRequestHandler<FailingStreamRequest, string>
+{
+	public async IAsyncEnumerable<string> HandleAsync(FailingStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return "Wait for it...";
+		throw new InvalidOperationException("Handler failed");
+	}
+}
+
+public class ExplicitGenericStreamRequest : IStreamRequest<string>
+{
+	public string Value { get; set; } = string.Empty;
+}
+
+public class ExplicitGenericStreamHandler<T> : IStreamRequestHandler<ExplicitGenericStreamRequest, string>
+{
+	async IAsyncEnumerable<string> IStreamRequestHandler<ExplicitGenericStreamRequest, string>.HandleAsync(ExplicitGenericStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken ct)
+	{
+		yield return $"{request.Value}-ExplicitHandled";
+	}
+}
+
+public class AmbiguousStreamRequest : IStreamRequest<string>
+{
+}
+
+public class AmbiguousStreamHandler : IStreamRequestHandler<AmbiguousStreamRequest, string>
+{
+	// Public method with the same name and signature
+	public async IAsyncEnumerable<string> HandleAsync(AmbiguousStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return "Public-Handled";
+	}
+
+	// Explicit interface implementation
+	async IAsyncEnumerable<string> IStreamRequestHandler<AmbiguousStreamRequest, string>.HandleAsync(AmbiguousStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return "Interface-Handled";
+	}
+}
+
+public class OpenStreamRequest : IStreamRequest<string>
+{
+	public string Data { get; set; } = string.Empty;
+}
+
+public class InheritedStreamRequest : OpenStreamRequest
+{
+}
+
+public class DeepDerivedStreamRequest : InheritedStreamRequest
+{
+	public int DeepValue { get; set; }
+}
+
+public class OpenStreamHandler<TRequest> : IStreamRequestHandler<TRequest, string>
+	where TRequest : OpenStreamRequest
+{
+	public async IAsyncEnumerable<string> HandleAsync(TRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"{request.Data}-Stream-0";
+		yield return $"{request.Data}-Stream-1";
+	}
+}
+
+public class ConstrainedStreamRequest : IStreamRequest<string>
+{
+	public int Value { get; set; }
+}
+
+public class ConstrainedStreamHandler<TRequest> : IStreamRequestHandler<TRequest, string>
+	where TRequest : ConstrainedStreamRequest
+{
+	public async IAsyncEnumerable<string> HandleAsync(TRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"{request.Value}-Constrained-0";
+		yield return $"{request.Value}-Constrained-1";
+	}
+}
+
+public class UnhandledStreamRequest : IStreamRequest<string>
+{
+}
+
+public class DerivedStreamRequest : IStreamRequest<string>
+{
+	public int Value { get; set; }
+}
+
+public abstract class BaseStreamHandler<TRequest> : IStreamRequestHandler<TRequest, string>
+	where TRequest : IStreamRequest<string>
+{
+	public abstract IAsyncEnumerable<string> HandleAsync(TRequest request, CancellationToken cancellationToken);
+}
+
+public class DerivedStreamHandler : BaseStreamHandler<DerivedStreamRequest>
+{
+	public override async IAsyncEnumerable<string> HandleAsync(DerivedStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"Derived: {request.Value}-0";
+		yield return $"Derived: {request.Value}-1";
+	}
+}
+
+public interface INamedStreamRequest : IStreamRequest<string>
+{
+	string Name { get; }
+}
+
+public class InterfaceInheritedStreamRequest : INamedStreamRequest
+{
+	public string Name { get; set; } = string.Empty;
+}
+
+public class AnotherNamedStreamRequest : INamedStreamRequest
+{
+	public string Name { get; set; } = string.Empty;
+}
+
+public class InterfaceInheritedStreamHandler : IStreamRequestHandler<InterfaceInheritedStreamRequest, string>
+{
+	public async IAsyncEnumerable<string> HandleAsync(InterfaceInheritedStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"{request.Name}-InterfaceHandled-0";
+		yield return $"{request.Name}-InterfaceHandled-1";
+	}
+}
+
+public class InterfaceConstrainedStreamHandler<TRequest> : IStreamRequestHandler<TRequest, string>
+	where TRequest : INamedStreamRequest
+{
+	public async IAsyncEnumerable<string> HandleAsync(TRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"{request.Name}-ConstrainedByInterface-0";
+		yield return $"{request.Name}-ConstrainedByInterface-1";
+	}
+}
+
+public class WrapperStreamRequest<T> : IStreamRequest<string>
+{
+	public T Item { get; set; } = default!;
+}
+
+public class WrapperStreamHandler<T> : IStreamRequestHandler<WrapperStreamRequest<T>, string>
+{
+	public async IAsyncEnumerable<string> HandleAsync(WrapperStreamRequest<T> request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return $"Handled-{request.Item}-0";
+		yield return $"Handled-{request.Item}-1";
+	}
+}
+
+public class MultiInterfaceStreamRequest : IStreamRequest<int>, IStreamRequest<string>
+{
+}
+
+public class MultiInterfaceStreamHandler : IStreamRequestHandler<MultiInterfaceStreamRequest, int>, IStreamRequestHandler<MultiInterfaceStreamRequest, string>
+{
+	public async IAsyncEnumerable<int> HandleAsync(MultiInterfaceStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		yield return 1;
+		yield return 2;
+	}
+
+	async IAsyncEnumerable<string> IStreamRequestHandler<MultiInterfaceStreamRequest, string>.HandleAsync(MultiInterfaceStreamRequest request, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken ct)
+	{
+		yield return "One";
+		yield return "Two";
+	}
+}

src/Request/Geekeey.Request.csproj

@@ -0,0 +1,36 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <IsPackable>true</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <RootNamespace>Geekeey.Request</RootNamespace>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup Condition="'$(Configuration)' == 'Debug'">
+    <InternalsVisibleTo Include="Geekeey.Request.Tests" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <PackageReadmeFile>package-readme.md</PackageReadmeFile>
+    <PackageIcon>package-icon.png</PackageIcon>
+    <PackageProjectUrl>https://code.geekeey.de/geekeey/request/src/branch/main/src/request</PackageProjectUrl>
+    <PackageLicenseExpression>EUPL-1.2</PackageLicenseExpression>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Include=".\package-icon.png" Pack="true" PackagePath="\" Visible="false" />
+    <None Include=".\package-readme.md" Pack="true" PackagePath="\" Visible="false" />
+    <None Include="..\..\LICENSE.md" Pack="true" PackagePath="\" Visible="false" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.Options" />
+  </ItemGroup>
+
+</Project>

src/Request/IRequestDispatcher.cs

@@ -0,0 +1,28 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Defines functionality to dispatch requests to their corresponding handlers.
+/// </summary>
+public interface IRequestDispatcher
+{
+	/// <summary>
+	/// Asynchronously send a request to a handler producing a scalar value.
+	/// </summary>
+	/// <param name="request">Request object</param>
+	/// <param name="cancellationToken">Optional cancellation token</param>
+	/// <typeparam name="TResponse">Response type</typeparam>
+	/// <returns>A task that represents the send operation. The task result contains the handler response</returns>
+	Task<TResponse> DispatchAsync<TResponse>(IScalarRequest<TResponse> request, CancellationToken cancellationToken = default);
+
+	/// <summary>
+	/// Asynchronously send a request to a handler producing a stream value.
+	/// </summary>
+	/// <param name="request">Request object</param>
+	/// <param name="cancellationToken">Optional cancellation token</param>
+	/// <typeparam name="TResponse">Response type</typeparam>
+	/// <returns>The created async enumerable, representing the stream of responses.</returns>
+	IAsyncEnumerable<TResponse> DispatchAsync<TResponse>(IStreamRequest<TResponse> request, CancellationToken cancellationToken = default);
+}

src/Request/IRequestDispatcherBuilder.cs

@@ -0,0 +1,19 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Represents a builder for configuring and registering request dispatchers and their related components.
+/// </summary>
+public interface IRequestDispatcherBuilder
+{
+	/// <summary>
+	/// Gets the <see cref="IServiceCollection"/> associated with the request dispatcher builder.
+	/// Provides access to the underlying service collection for configuring dependencies
+	/// and registering services required by the request dispatcher.
+	/// </summary>
+	IServiceCollection Services { get; }
+}

src/Request/IScalarPipelineBehavior.cs

@@ -0,0 +1,34 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+#pragma warning disable CA1711
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Represents a behavior in the request pipeline, allowing interception, modification,
+/// or chaining of asynchronous stream requests and responses.
+/// </summary>
+/// <typeparam name="TRequest">The type of the request being handled. Must implement <see cref="IScalarRequest{TResponse}"/>.</typeparam>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+public interface IScalarRequestBehavior<in TRequest, TResponse> where TRequest : IScalarRequest<TResponse>
+{
+	/// <summary>
+	/// Handles the asynchronous processing of a request, allowing behavior customization
+	/// such as interception, modification, or chaining of the request and its response.
+	/// </summary>
+	/// <param name="request">The request instance being processed.</param>
+	/// <param name="next">The next delegate in the pipeline to execute after the custom behavior.</param>
+	/// <param name="cancellationToken">A token to monitor for cancellation requests.</param>
+	/// <returns>A task that represents the asynchronous operation. The task result contains the response from the request.</returns>
+	Task<TResponse> HandleAsync(TRequest request, ScalarHandlerDelegate<TResponse> next, CancellationToken cancellationToken);
+}
+
+/// <summary>
+/// Represents the delegate responsible for handling asynchronous requests in a pipeline.
+/// </summary>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+/// <param name="request">The asynchronous request being processed.</param>
+/// <param name="cancellationToken">A token for monitoring cancellation requests.</param>
+/// <returns>A task, that represents the asynchronous operation, containing the response of type <typeparamref name="TResponse"/>.</returns>
+public delegate Task<TResponse> ScalarHandlerDelegate<TResponse>(IScalarRequest<TResponse> request, CancellationToken cancellationToken);

src/Request/IScalarRequest.cs

@@ -0,0 +1,14 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Represents a request that produces a response of a specified type.
+/// This interface serves as a marker for distinguishing request types,
+/// enabling their integration into request-based pipelines or dispatch mechanisms.
+/// </summary>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+public interface IScalarRequest<out TResponse>
+{
+}

src/Request/IScalarRequestHandler.cs

@@ -0,0 +1,20 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Defines a handler for processing requests of a specific type and returning a response.
+/// </summary>
+/// <typeparam name="TRequest">The type of the request to be handled. Must implement <see cref="IScalarRequest{TResponse}"/>.</typeparam>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+public interface IScalarRequestHandler<in TRequest, TResponse> where TRequest : IScalarRequest<TResponse>
+{
+	/// <summary>
+	/// Processes a scalar request and returns a response asynchronously.
+	/// </summary>
+	/// <param name="request">The request object to be processed.</param>
+	/// <param name="cancellationToken">A token to observe for cancellation requests.</param>
+	/// <returns>A task representing the asynchronous operation, containing the response of type <typeparamref name="TResponse"/>.</returns>
+	Task<TResponse> HandleAsync(TRequest request, CancellationToken cancellationToken = default);
+}

src/Request/IStreamPipelineBehavior.cs

@@ -0,0 +1,34 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+#pragma warning disable CA1711
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Represents a behavior in the request pipeline, allowing interception, modification,
+/// or chaining of asynchronous stream requests and responses.
+/// </summary>
+/// <typeparam name="TRequest">The type of the request being processed. Must implement <see cref="IStreamRequest{TResponse}"/>.</typeparam>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+public interface IStreamRequestBehavior<in TRequest, TResponse> where TRequest : IStreamRequest<TResponse>
+{
+	/// <summary>
+	/// Handles the asynchronous processing of a request, allowing behavior customization
+	/// such as interception, modification, or chaining of the request and its response.
+	/// </summary>
+	/// <param name="request">The request instance being processed.</param>
+	/// <param name="next">The next delegate in the pipeline to execute after the custom behavior.</param>
+	/// <param name="cancellationToken">A token to monitor for cancellation requests.</param>
+	/// <returns>An asynchronous stream of <typeparamref name="TResponse"/> representing the processed response.</returns>
+	IAsyncEnumerable<TResponse> HandleAsync(TRequest request, StreamHandlerDelegate<TResponse> next, CancellationToken cancellationToken);
+}
+
+/// <summary>
+/// Represents the delegate responsible for handling asynchronous requests in a pipeline.
+/// </summary>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+/// <param name="request">The asynchronous request being processed.</param>
+/// <param name="cancellationToken">A token for monitoring cancellation requests.</param>
+/// <returns>An asynchronous stream of responses of type <typeparamref name="TResponse"/>.</returns>
+public delegate IAsyncEnumerable<TResponse> StreamHandlerDelegate<TResponse>(IStreamRequest<TResponse> request, CancellationToken cancellationToken);

src/Request/IStreamRequest.cs

@@ -0,0 +1,14 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Represents a request that produces a response of a specified type.
+/// This interface serves as a marker for distinguishing request types,
+/// enabling their integration into request-based pipelines or dispatch mechanisms.
+/// </summary>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+public interface IStreamRequest<out TResponse>
+{
+}

src/Request/IStreamRequestHandler.cs

@@ -0,0 +1,21 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Defines a handler for processing streaming requests of a specific type and producing
+/// a stream of responses.
+/// </summary>
+/// <typeparam name="TRequest">The type of the request to handle. This must implement <see cref="IStreamRequest{TResponse}"/>.</typeparam>
+/// <typeparam name="TResponse">The type of the response produced by the implementing request handler.</typeparam>
+public interface IStreamRequestHandler<in TRequest, out TResponse> where TRequest : IStreamRequest<TResponse>
+{
+	/// <summary>
+	/// Handles a streaming request and returns a stream of responses asynchronously.
+	/// </summary>
+	/// <param name="request">The request object to be processed.</param>
+	/// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+	/// <returns>An asynchronous stream of responses of type <typeparamref name="TResponse"/>.</returns>
+	IAsyncEnumerable<TResponse> HandleAsync(TRequest request, CancellationToken cancellationToken);
+}

src/Request/RequestDispatcher.cs

@@ -0,0 +1,48 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Collections.Concurrent;
+using System.Reflection.Metadata;
+
+[assembly: MetadataUpdateHandler(typeof(Geekeey.Request.RequestDispatcher))]
+
+namespace Geekeey.Request;
+
+internal sealed class RequestDispatcher : IRequestDispatcher
+{
+	private static readonly ConcurrentDictionary<(Type, Type), ScalarRequestInvoker> ScalarRequestHandlers = new();
+	private static readonly ConcurrentDictionary<(Type, Type), StreamRequestInvoker> StreamRequestHandlers = new();
+
+	private readonly IServiceProvider _serviceProvider;
+
+	public RequestDispatcher(IServiceProvider serviceProvider)
+	{
+		_serviceProvider = serviceProvider;
+	}
+
+	public Task<TResponse> DispatchAsync<TResponse>(IScalarRequest<TResponse> request, CancellationToken cancellationToken = default)
+	{
+		ArgumentNullException.ThrowIfNull(request);
+
+		var handler = ScalarRequestHandlers.GetOrAdd((request.GetType(), typeof(TResponse)), static key =>
+		{
+			var type = typeof(ScalarRequestInvoker<,>).MakeGenericType(key.Item1, key.Item2);
+			return (ScalarRequestInvoker)Activator.CreateInstance(type)!;
+		});
+
+		return ((ScalarRequestInvoker<TResponse>)handler).HandleAsync(request, _serviceProvider, cancellationToken);
+	}
+
+	public IAsyncEnumerable<TResponse> DispatchAsync<TResponse>(IStreamRequest<TResponse> request, CancellationToken cancellationToken = default)
+	{
+		ArgumentNullException.ThrowIfNull(request);
+
+		var handler = StreamRequestHandlers.GetOrAdd((request.GetType(), typeof(TResponse)), static key =>
+		{
+			var type = typeof(StreamRequestInvoker<,>).MakeGenericType(key.Item1, key.Item2);
+			return (StreamRequestInvoker)Activator.CreateInstance(type)!;
+		});
+
+		return ((StreamRequestInvoker<TResponse>)handler).HandleAsync(request, _serviceProvider, cancellationToken);
+	}
+}

src/Request/RequestDispatcherBuilderExtensions.cs

@@ -0,0 +1,133 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Reflection;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
+using static Geekeey.Request.RequestDispatcherOptions;
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Provides extension methods for configuring <see cref="IRequestDispatcherBuilder"/>
+/// with additional capabilities such as searching and registering request handlers in assemblies or adding types directly.
+/// </summary>
+public static class RequestDispatcherBuilderExtensions
+{
+	/// <summary>
+	/// Searches for request handler types within the specified assembly and adds them to the request dispatcher
+	/// configuration.
+	/// </summary>
+	/// <param name="builder">The <see cref="IRequestDispatcherBuilder"/> to configure.</param>
+	/// <param name="assembly">The assembly to search for request handler types.</param>
+	/// <returns>The <see cref="IRequestDispatcherBuilder"/> instance for further configuration.</returns>
+	public static IRequestDispatcherBuilder SearchHandlerInAssembly(this IRequestDispatcherBuilder builder, Assembly assembly)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		var exports = assembly.GetTypes()
+			.Where(type => type is { IsClass: true, IsAbstract: false })
+			.Where(IsRequestHandlerType);
+
+		builder.Add(exports);
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Searches for request handler types within the specified assembly and adds them to the request dispatcher
+	/// configuration with the given service lifetime.
+	/// </summary>
+	/// <param name="builder">The <see cref="IRequestDispatcherBuilder"/> to configure.</param>
+	/// <param name="assembly">The assembly to search for request handler types.</param>
+	/// <param name="lifetime">The lifetime with which the request handlers are registered in the dependency injection container.</param>
+	/// <returns>The <see cref="IRequestDispatcherBuilder"/> instance for further configuration.</returns>
+	public static IRequestDispatcherBuilder SearchHandlerInAssembly(this IRequestDispatcherBuilder builder, Assembly assembly, ServiceLifetime lifetime)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		var exports = assembly.GetTypes()
+			.Where(type => type is { IsClass: true, IsAbstract: false })
+			.Where(IsRequestHandlerType);
+
+		builder.Add(exports, lifetime);
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified type to the request dispatcher configuration for inspection.
+	/// </summary>
+	/// <param name="builder">The <see cref="IRequestDispatcherBuilder"/> to configure.</param>
+	/// <param name="type">The type to be added to the request dispatcher configuration.</param>
+	/// <returns>The <see cref="IRequestDispatcherBuilder"/> instance for further configuration.</returns>
+	public static IRequestDispatcherBuilder Add(this IRequestDispatcherBuilder builder, Type type)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		builder.Services.AddOptions<RequestDispatcherOptions>()
+			.Configure(options => options.Inspect([type]));
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified type to the request dispatcher configuration.
+	/// This also adds the type to the service collection with the specified lifetime,
+	/// allowing it to be resolved as a dependency in request handlers and behaviors.
+	/// </summary>
+	/// <param name="builder">The <see cref="IRequestDispatcherBuilder"/> used to configure the request dispatcher.</param>
+	/// <param name="type">The type to be added to the request dispatcher configuration.</param>
+	/// <param name="lifetime">The lifetime scope of the type in the service container.</param>
+	/// <returns>The <see cref="IRequestDispatcherBuilder"/> instance for further configuration.</returns>
+	public static IRequestDispatcherBuilder Add(this IRequestDispatcherBuilder builder, Type type, ServiceLifetime lifetime)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		builder.Services.AddOptions<RequestDispatcherOptions>()
+			.Configure(options => options.Inspect([type]));
+
+		builder.Services.Add(new ServiceDescriptor(type, type, lifetime));
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified collection of types to the request dispatcher configuration for inspection.
+	/// </summary>
+	/// <param name="builder">The <see cref="IRequestDispatcherBuilder"/> to configure.</param>
+	/// <param name="type">The collection of types to be added to the request dispatcher configuration.</param>
+	/// <returns>The <see cref="IRequestDispatcherBuilder"/> instance for further configuration.</returns>
+	public static IRequestDispatcherBuilder Add(this IRequestDispatcherBuilder builder, IEnumerable<Type> type)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		builder.Services.AddOptions<RequestDispatcherOptions>()
+			.Configure(options => options.Inspect(type));
+
+		return builder;
+	}
+
+	/// <summary>
+	/// Adds the specified collection of types to the request dispatcher configuration for inspection.
+	/// This also adds the specified collection of types to the service collection with the specified lifetime,
+	/// allowing it to be resolved as a dependency in request handlers and behaviors.
+	/// </summary>
+	/// <param name="builder">The <see cref="IRequestDispatcherBuilder"/> to configure.</param>
+	/// <param name="type">The collection of types to be added to the request dispatcher configuration.</param>
+	/// <param name="lifetime">The lifetime scope of the types in the service container.</param>
+	/// <returns>The <see cref="IRequestDispatcherBuilder"/> instance for further configuration.</returns>
+	public static IRequestDispatcherBuilder Add(this IRequestDispatcherBuilder builder, IEnumerable<Type> type, ServiceLifetime lifetime)
+	{
+		ArgumentNullException.ThrowIfNull(builder);
+
+		builder.Services.AddOptions<RequestDispatcherOptions>()
+			.Configure(options => options.Inspect(type));
+
+		builder.Services.Add(type.Select(export => new ServiceDescriptor(export, export, lifetime)));
+
+		return builder;
+	}
+}

src/Request/RequestDispatcherOptions.cs

@@ -0,0 +1,207 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Collections;
+using System.Collections.Concurrent;
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Geekeey.Request;
+
+internal sealed class RequestDispatcherOptions
+{
+	private readonly List<Type> _search = [];
+	private readonly Lazy<TypeIndex> _behaviorsTypeIndex;
+	private readonly Lazy<TypeIndex> _handlersTypeIndex;
+
+	public RequestDispatcherOptions()
+	{
+		_behaviorsTypeIndex = new Lazy<TypeIndex>(() => new BehaviorTypeIndex(_search.Distinct()));
+		_handlersTypeIndex = new Lazy<TypeIndex>(() => new HandlerTypeIndex(_search.Distinct()));
+	}
+
+	public void Inspect(IEnumerable<Type> assembly)
+	{
+		if (_behaviorsTypeIndex.IsValueCreated || _handlersTypeIndex.IsValueCreated)
+		{
+			throw new InvalidOperationException("The type index has already been created. Cannot inspect new assemblies.");
+		}
+
+		_search.AddRange(assembly);
+	}
+
+	public IEnumerable<T> GetRequestBehaviors<T>(IServiceProvider services)
+	{
+		return _behaviorsTypeIndex.Value.Resolve<T>(services);
+	}
+
+	public IEnumerable<T> GetRequestHandlers<T>(IServiceProvider services)
+	{
+		return _handlersTypeIndex.Value.Resolve<T>(services);
+	}
+
+	private abstract class TypeIndex
+	{
+		private readonly ConcurrentDictionary<Type, Func<IServiceProvider, IEnumerable>> _cache = new();
+
+		protected readonly Dictionary<Type, List<Type>> _closedTypeInfo = [];
+		protected readonly List<Type> _openTypeInfo = [];
+
+		protected TypeIndex(IEnumerable<Type> collection, Func<Type, bool> predicate)
+		{
+			foreach (var type in collection)
+			{
+				if (type.IsGenericTypeDefinition)
+				{
+					if (type.GetInterfaces().Any(predicate))
+					{
+						_openTypeInfo.Add(type);
+					}
+				}
+				else
+				{
+					foreach (var @interface in type.GetInterfaces().Where(predicate))
+					{
+						(_closedTypeInfo.TryGetValue(@interface, out var list) ? list : _closedTypeInfo[@interface] = []).Add(type);
+					}
+				}
+			}
+		}
+
+		public IEnumerable<T> Resolve<T>(IServiceProvider services)
+		{
+			return (IEnumerable<T>)_cache.GetOrAdd(typeof(T), CreateResolverFactory<T>)(services);
+		}
+
+		protected abstract IReadOnlyList<Type> IsAssignableTo(Type type);
+
+		private Func<IServiceProvider, IEnumerable<T>> CreateResolverFactory<T>(Type @interface)
+		{
+			var list = IsAssignableTo(@interface);
+			return ResolverFactory;
+
+			IEnumerable<T> ResolverFactory(IServiceProvider services)
+			{
+				foreach (var type in list)
+				{
+					yield return (T)ActivatorUtilities.GetServiceOrCreateInstance(services, type);
+				}
+			}
+		}
+	}
+
+	internal static bool IsRequestHandlerType(Type type)
+	{
+		return type.IsGenericType &&
+			   (type.GetGenericTypeDefinition() == typeof(IScalarRequestHandler<,>) ||
+				type.GetGenericTypeDefinition() == typeof(IStreamRequestHandler<,>));
+	}
+
+	private sealed class HandlerTypeIndex(IEnumerable<Type> collection)
+		: TypeIndex(collection, IsRequestHandlerType)
+	{
+		protected override IReadOnlyList<Type> IsAssignableTo(Type @interface)
+		{
+			var result = new List<Type>();
+
+			if (_closedTypeInfo.TryGetValue(@interface, out var list))
+			{
+				result.AddRange(list);
+			}
+
+			var requestType = @interface.GetGenericArguments()[0];
+			_ = @interface.GetGenericArguments()[1];
+
+			foreach (var type in _openTypeInfo)
+			{
+				try
+				{
+					// open type case one: Handler<TRequest> : IRequestHandler<TRequest, TOutput>
+					// We try to close it with the request type.
+					var impl = type.MakeGenericType(requestType);
+					if (impl.IsAssignableTo(@interface))
+					{
+						result.Add(impl);
+					}
+				}
+				catch (ArgumentException)
+				{
+				}
+
+				try
+				{
+					// open type case two: Handler<T> : IRequestHandler<WrapperRequest<T>, TOutput>
+					// If the request is generic, we try to close the handler with the request's generic arguments.
+					if (requestType.IsGenericType)
+					{
+						var impl = type.MakeGenericType(requestType.GetGenericArguments());
+						if (impl.IsAssignableTo(@interface))
+						{
+							result.Add(impl);
+						}
+					}
+				}
+				catch (ArgumentException)
+				{
+				}
+			}
+
+			return result;
+		}
+	}
+
+	internal static bool IsRequestBehaviorType(Type type)
+	{
+		return type.IsGenericType &&
+			   (type.GetGenericTypeDefinition() == typeof(IScalarRequestBehavior<,>) ||
+				type.GetGenericTypeDefinition() == typeof(IStreamRequestBehavior<,>));
+	}
+
+	private sealed class BehaviorTypeIndex(IEnumerable<Type> collection)
+		: TypeIndex(collection, IsRequestBehaviorType)
+	{
+		protected override IReadOnlyList<Type> IsAssignableTo(Type @interface)
+		{
+			var result = new List<Type>();
+
+			if (_closedTypeInfo.TryGetValue(@interface, out var list))
+			{
+				result.AddRange(list);
+			}
+
+			var requestType = @interface.GetGenericArguments()[0];
+			var responseType = @interface.GetGenericArguments()[1];
+
+			foreach (var behaviour in _openTypeInfo)
+			{
+				try
+				{
+					// open type case one: Behaviour<TRequest, TResponse> : IRequestBehaviour<TRequest, TResponse>
+					var impl = behaviour.MakeGenericType(requestType, responseType);
+					if (impl.IsAssignableTo(@interface))
+					{
+						result.Add(impl);
+					}
+				}
+				catch (ArgumentException)
+				{
+				}
+
+				try
+				{
+					// open type case two: Behaviour<T> : IRequestBehaviour<WrapperRequest<T>, TResponse>
+					var impl = behaviour.MakeGenericType(requestType.GetGenericArguments());
+					if (impl.IsAssignableTo(@interface))
+					{
+						result.Add(impl);
+					}
+				}
+				catch (ArgumentException)
+				{
+				}
+			}
+
+			return result;
+		}
+	}
+}

src/Request/ScalarRequestInvoker.cs

@@ -0,0 +1,47 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+namespace Geekeey.Request;
+
+internal abstract class ScalarRequestInvoker
+{
+	public abstract Task<object?> HandleAsync(object request, IServiceProvider serviceProvider, CancellationToken cancellationToken);
+}
+
+internal abstract class ScalarRequestInvoker<TResponse> : ScalarRequestInvoker
+{
+	public abstract Task<TResponse> HandleAsync(IScalarRequest<TResponse> request, IServiceProvider serviceProvider, CancellationToken cancellationToken);
+}
+
+internal sealed class ScalarRequestInvoker<TRequest, TResponse> : ScalarRequestInvoker<TResponse>
+	where TRequest : IScalarRequest<TResponse>
+{
+	public override async Task<object?> HandleAsync(object request, IServiceProvider serviceProvider, CancellationToken cancellationToken)
+	{
+		return await HandleAsync((IScalarRequest<TResponse>)request, serviceProvider, cancellationToken).ConfigureAwait(false);
+	}
+
+	public override Task<TResponse> HandleAsync(IScalarRequest<TResponse> request, IServiceProvider serviceProvider, CancellationToken cancellationToken)
+	{
+		var options = serviceProvider.GetRequiredService<IOptions<RequestDispatcherOptions>>().Value;
+
+		var pipeline = options.GetRequestBehaviors<IScalarRequestBehavior<TRequest, TResponse>>(serviceProvider)
+			.Reverse()
+			.Aggregate((ScalarHandlerDelegate<TResponse>)Head, Chain);
+
+		return pipeline(request, cancellationToken);
+
+		static ScalarHandlerDelegate<TResponse> Chain(ScalarHandlerDelegate<TResponse> next, IScalarRequestBehavior<TRequest, TResponse> filter)
+		{
+			return (req, ct) => filter.HandleAsync((TRequest)req, next, ct);
+		}
+
+		Task<TResponse> Head(IScalarRequest<TResponse> r, CancellationToken ct)
+		{
+			return options.GetRequestHandlers<IScalarRequestHandler<TRequest, TResponse>>(serviceProvider).First().HandleAsync((TRequest)r, ct);
+		}
+	}
+}

src/Request/ServiceCollectionExtensions.cs

@@ -0,0 +1,50 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
+namespace Geekeey.Request;
+
+/// <summary>
+/// Provides extension methods for configuring and registering request dispatchers and their dependencies.
+/// </summary>
+public static class ServiceCollectionExtensions
+{
+	/// <summary>
+	/// Adds the request dispatcher services to the specified <see cref="IServiceCollection"/>.
+	/// </summary>
+	/// <param name="services">The service collection to which the request dispatcher services will be added.</param>
+	/// <returns>An instance of <see cref="IRequestDispatcherBuilder"/> to configure the request dispatcher.</returns>
+	public static IRequestDispatcherBuilder AddRequestDispatcher(this IServiceCollection services)
+	{
+		ArgumentNullException.ThrowIfNull(services);
+
+		services.AddOptions<RequestDispatcherOptions>();
+		services.TryAddTransient<IRequestDispatcher, RequestDispatcher>();
+
+		return new RequestDispatcherBuilder(services);
+	}
+
+	/// <summary>
+	/// Adds the request dispatcher services to the specified <see cref="IServiceCollection"/>
+	/// and configures it using the provided <see cref="Action{T}"/>.
+	/// </summary>
+	/// <param name="services">The service collection to which the request dispatcher services will be added.</param>
+	/// <param name="configure">A delegate to configure the request dispatcher builder.</param>
+	/// <returns>The service collection with the request dispatcher services added.</returns>
+	public static IServiceCollection AddRequestDispatcher(this IServiceCollection services, Action<IRequestDispatcherBuilder> configure)
+	{
+		ArgumentNullException.ThrowIfNull(services);
+		ArgumentNullException.ThrowIfNull(configure);
+
+		configure(services.AddRequestDispatcher());
+
+		return services;
+	}
+
+	private sealed class RequestDispatcherBuilder(IServiceCollection services) : IRequestDispatcherBuilder
+	{
+		public IServiceCollection Services { get; } = services;
+	}
+}

src/Request/StreamRequestInvoker.cs

@@ -0,0 +1,52 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Runtime.CompilerServices;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+namespace Geekeey.Request;
+
+internal abstract class StreamRequestInvoker
+{
+	public abstract IAsyncEnumerable<object?> HandleAsync(object request, IServiceProvider serviceProvider, CancellationToken cancellationToken);
+}
+
+internal abstract class StreamRequestInvoker<TResponse> : StreamRequestInvoker
+{
+	public abstract IAsyncEnumerable<TResponse> HandleAsync(IStreamRequest<TResponse> request, IServiceProvider serviceProvider, CancellationToken cancellationToken);
+}
+
+internal sealed class StreamRequestInvoker<TRequest, TResponse> : StreamRequestInvoker<TResponse>
+	where TRequest : IStreamRequest<TResponse>
+{
+	public override async IAsyncEnumerable<object?> HandleAsync(object request, IServiceProvider serviceProvider, [EnumeratorCancellation] CancellationToken cancellationToken)
+	{
+		await foreach (var item in HandleAsync((IStreamRequest<TResponse>)request, serviceProvider, cancellationToken))
+		{
+			yield return item;
+		}
+	}
+
+	public override IAsyncEnumerable<TResponse> HandleAsync(IStreamRequest<TResponse> request, IServiceProvider serviceProvider, CancellationToken cancellationToken)
+	{
+		var options = serviceProvider.GetRequiredService<IOptions<RequestDispatcherOptions>>().Value;
+
+		var pipeline = options.GetRequestBehaviors<IStreamRequestBehavior<TRequest, TResponse>>(serviceProvider)
+			.Reverse()
+			.Aggregate((StreamHandlerDelegate<TResponse>)Head, Chain);
+
+		return pipeline(request, cancellationToken);
+
+		static StreamHandlerDelegate<TResponse> Chain(StreamHandlerDelegate<TResponse> next, IStreamRequestBehavior<TRequest, TResponse> filter)
+		{
+			return (req, ct) => filter.HandleAsync((TRequest)req, next, ct);
+		}
+
+		IAsyncEnumerable<TResponse> Head(IStreamRequest<TResponse> r, CancellationToken ct)
+		{
+			return options.GetRequestHandlers<IStreamRequestHandler<TRequest, TResponse>>(serviceProvider).First().HandleAsync((TRequest)r, ct);
+		}
+	}
+}