Something

namespace Cecil.Debug
{

	using System;
	using System.IO;
	using SR = System.Reflection;

	using Mono.Cecil;
	using Mono.Cecil.Cil;

	public class Create
	{

		static void Main ()
		{
			AssemblyDefinition asm = AssemblyFactory.DefineAssembly ("Hello", AssemblyKind.Console);

			TypeDefinition prog = new TypeDefinition ("Program", string.Empty,
				TypeAttributes.Public, asm.MainModule.Import (typeof (object)));

			prog.Attributes |= TypeAttributes.BeforeFieldInit;

			MethodDefinition ctor = new MethodDefinition (MethodDefinition.Ctor, MethodAttributes.Public,
				asm.MainModule.Import (typeof (void)));

			ctor.Attributes |= MethodAttributes.SpecialName;
			ctor.Attributes |= MethodAttributes.RTSpecialName;
			ctor.Attributes |= MethodAttributes.HideBySig;

			ctor.Body.CilWorker.Emit (OpCodes.Ldarg_0);
			ctor.Body.CilWorker.Emit (OpCodes.Call, asm.MainModule.Import (typeof (object).GetConstructor (new Type[0])));
			ctor.Body.CilWorker.Emit (OpCodes.Ret);

			prog.Constructors.Add (ctor);

			MethodDefinition hello = new MethodDefinition ("Hello", MethodAttributes.Public,
				asm.MainModule.Import (typeof (void)));

			hello.Attributes |= MethodAttributes.HideBySig;

			hello.Body.CilWorker.Emit (OpCodes.Ldstr, "Hello World !");
			hello.Body.CilWorker.Emit (OpCodes.Call,
				asm.MainModule.Import (typeof (Console).GetMethod ("WriteLine", new Type[] { typeof (string) })));
			hello.Body.CilWorker.Emit (OpCodes.Ret);

			prog.Methods.Add (hello);

			MethodDefinition main = new MethodDefinition ("Main", MethodAttributes.Public | MethodAttributes.Static,
				asm.MainModule.Import (typeof (void)));

			main.Body.CilWorker.Emit (OpCodes.Newobj, ctor);
			main.Body.CilWorker.Emit (OpCodes.Call, hello);
			main.Body.CilWorker.Emit (OpCodes.Ret);

			prog.Methods.Add (main);

			asm.EntryPoint = main;

			asm.MainModule.Types.Add (prog);

			FileStream ms = new FileStream (asm.Name.Name+".dll" ,FileMode.Create,FileAccess.ReadWrite);

			AssemblyFactory.SaveAssembly (asm, ms);

			SR.Assembly srasm = SR.Assembly.Load (asm.Name.FullName);

			//SR.Assembly srasm = AssemblyFactory.CreateReflectionAssembly (asm);

			Type tprog = srasm.GetType ("Program");

			Console.WriteLine (tprog.FullName);

			object inst = Activator.CreateInstance (tprog);
			tprog.GetMethod ("Hello").Invoke (inst, new object[0]);

			Console.Read ();
		}
	}
}