This code gif an exception: Invocation exception, please help, I don't know what happen, I think is some thing with the Add because he work when I push onto the stack intergers, and when i push lvalue It's didn't work, thanks static void Main(string[] args) { AppDomain dominioAplicacion = System.Threading.Thread.GetDomain(); AssemblyName nombre_Del_Ensamblado = new AssemblyName("ASS"); AssemblyBuilder ensambladoBld = dominioAplicacion.DefineDynamicAssembly(nombre_Del_Ensamblado, AssemblyBuilderAccess.RunAndSave); ModuleBuilder moduloBld = ensambladoBld.DefineDynamicModule("<MOD"); TypeBuilder claseContenedoraBld = moduloBld.DefineType("claseContenedora"); MethodBuilder mainBld = claseContenedoraBld.DefineMethod("main", MethodAttributes.Public | MethodAttributes.Static, typeof(void), Type.EmptyTypes); ILGenerator il = mainBld.GetILGenerator(); FieldBuilder campoBld = claseContenedoraBld.DefineField("x", typeof(int), FieldAttributes.Public | FieldAttributes.Static); il.Emit(OpCodes.Ldc_I4, 2); il.Emit(OpCodes.Stsfld, campoBld); FieldBuilder campoBld1 = claseContenedoraBld.DefineField("x1", typeof(int), FieldAttributes.Public | FieldAttributes.Static); il.Emit(OpCodes.Ldc_I4, 2); il.Emit(OpCodes.Stsfld, campoBld1); il.Emit(OpCodes.Ldftn, campoBld); //il.Emit(OpCodes.Unbox, typeof(int)); //il.Emit(OpCodes.Stloc_0); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldftn, campoBld1); //il.Emit(OpCodes.Unbox, typeof(int)); il.Emit(OpCodes.Stloc_1); il.Emit(OpCodes.Ldloc_1); //il.Emit(OpCodes.Box, typeof(int)); //il.Emit(OpCodes.Ldftn, campoBld1); //il.Emit(OpCodes.Unbox, typeof(int)); il.Emit(OpCodes.Add); il.Emit(OpCodes.Pop); //il.Emit(OpCodes.Stsfld, campoBld1); il.Emit(OpCodes.Ret); Type t = claseContenedoraBld.CreateType(); object ptInstance = Activator.CreateInstance(t, new Type[] { }); t.InvokeMember("main", BindingFlags.InvokeMethod | BindingFlags.Static | BindingFlags.Public, null, ptInstance, new object[0]); var x = t.GetField("x"); }