gistfile1.cs

using System.Linq;
using System.Reflection;
using System.Reflection.Emit;

namespace DP115Test
{
	using System;

	class Program
	{
		static void Main(string[] args)
		{
			var assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName("Foo"), AssemblyBuilderAccess.RunAndSave);
			var type = assembly
				.DefineDynamicModule("FooModule", "FooModule.dll", true)
				.DefineType("AClass", TypeAttributes.Public | TypeAttributes.AutoClass | TypeAttributes.AnsiClass | TypeAttributes.BeforeFieldInit, typeof(object), new[] { typeof(IFoo) });
			var method = type.DefineMethod("IFoo.SomeMethod", MethodAttributes.Private | MethodAttributes.HideBySig | MethodAttributes.NewSlot | MethodAttributes.Virtual | MethodAttributes.Final, CallingConventions.HasThis);
			var typeParameters = method.DefineGenericParameters(new[] { "TBase", "TInherited" });
			typeParameters[1].SetBaseTypeConstraint(typeParameters[0]);
			type.DefineMethodOverride(method, typeof(IFoo).GetMethods().Single());
			ConstructorBuilder nestedCtor;
			MethodBuilder nestedMethod;
			TypeBuilder nested = GenerateInvocationType(type, method, out nestedCtor, out nestedMethod);
			GenerateSomeMethod(method, nested, typeParameters, nestedCtor, nestedMethod);
			var createdType = type.CreateType();
			nested.CreateType();
			assembly.Save("FooModule.dll");

			var instance = Activator.CreateInstance(createdType) as IFoo;
			//instance.SomeMethod<IComparable<string>, string>(); // NOTE: will currently yield StackOverflowException
		}

		private static TypeBuilder GenerateInvocationType(TypeBuilder type, MethodBuilder method, out ConstructorBuilder nestedCtor, out MethodBuilder nestedMethod)
		{
			var builder = type.DefineNestedType("NestedClass",
			                                    TypeAttributes.AutoLayout | TypeAttributes.AnsiClass |
			                                    TypeAttributes.Serializable |
			                                    TypeAttributes.Sealed | TypeAttributes.NestedAssembly, typeof (object),
			                                    new[] {typeof (IInvocation)});
			var typeParameters = builder.DefineGenericParameters(new[] {"TBase_NestedType", "TInherited_NestedType"});
			typeParameters[1].SetBaseTypeConstraint(typeParameters[0]);
			var target = builder.DefineField("target", type, FieldAttributes.InitOnly | FieldAttributes.Private);
			nestedCtor = GenerateCtor(type, builder, target);
			nestedMethod = GenerateInvokeOnTarget(type, builder, target, typeParameters, method);
			return builder;
		}

		private static MethodBuilder GenerateInvokeOnTarget(TypeBuilder type, TypeBuilder builder, FieldBuilder target, GenericTypeParameterBuilder[] parameters, MethodBuilder methodToInvoke)
		{
			var method = builder.DefineMethod("InvokeOnTarget",
			                                  MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.NewSlot |
			                                  MethodAttributes.Virtual | MethodAttributes.Final, CallingConventions.HasThis);
			method.SetReturnType(typeof(void));
			var generator = method.GetILGenerator();
			generator.Emit(OpCodes.Ldarg_0);
			generator.Emit(OpCodes.Ldfld, target);
			generator.Emit(OpCodes.Callvirt, methodToInvoke.MakeGenericMethod(parameters));
			generator.Emit(OpCodes.Ret);
			return method;
		}

		private static ConstructorBuilder GenerateCtor(TypeBuilder type, TypeBuilder builder, FieldBuilder target)
		{
			var constructor =
				builder.DefineConstructor(MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.RTSpecialName,
				                          CallingConventions.HasThis, new Type[] {type});
			var generator = constructor.GetILGenerator();
			generator.Emit(OpCodes.Ldarg_0);
			generator.Emit(OpCodes.Call, typeof (object).GetConstructors().Single());
			generator.Emit(OpCodes.Ldarg_0);
			generator.Emit(OpCodes.Ldarg_1);
			generator.Emit(OpCodes.Stfld, target);
			generator.Emit(OpCodes.Ret);
			return constructor;
		}

		private static void GenerateSomeMethod(MethodBuilder method, TypeBuilder invocation, GenericTypeParameterBuilder[] parameters, ConstructorBuilder nestedCtor, MethodBuilder nestedMethod)
		{
			method.SetReturnType(typeof(void));

			var genericType = invocation.MakeGenericType(parameters);
			var constructor = TypeBuilder.GetConstructor(genericType, nestedCtor);
			var methodInfo = TypeBuilder.GetMethod(genericType,nestedMethod);
			var generator = method.GetILGenerator();
			generator.Emit(OpCodes.Ldarg_0);
			generator.Emit(OpCodes.Newobj, constructor);
			generator.Emit(OpCodes.Callvirt, methodInfo);
			generator.Emit(OpCodes.Ret);
		}
	}

	public interface IFoo
	{
		void SomeMethod<TBase, TInherited>() where TInherited : TBase;
	}

	public interface IInvocation
	{
		void InvokeOnTarget();
	}
}