该段IL代码如何用Emit 生成

这样写

        var method = typeBldr.DefineMethod("GetIdValue"
            , MethodAttributes.Family | MethodAttributes.HideBySig
            | MethodAttributes.Virtual);
        method.SetReturnType(typeof(object));
        ILGenerator methodIL = method.GetILGenerator();
        methodIL.Emit(OpCodes.Nop);
        methodIL.Emit(OpCodes.Ldarg_0);
         methodIL.Emit(OpCodes.Ldstr, "ID");
        var indexerDictionary = typeof(Csla.Core.BusinessBase);
        methodIL.Emit(OpCodes.Call, indexerDictionary.GetMethod("get_Item", new Type[] { typeof(string) }));
        methodIL.Emit(OpCodes.Stloc_0);
        methodIL.Emit(OpCodes.Br_S, "IL_000f");
        methodIL.Emit(OpCodes.Ldloc_0);
        methodIL.Emit(OpCodes.Ret);

一直不成功不知什么原因，请教大师们