用INotifyPropertyChanged实现Reflection.Emit

Question

使用C#/.Net 4.0，我将数据存储在一个BindingList中，其中dataRow是通过Reflection.Emit在运行时定义的。(传入数据的结构各不相同，由外部源定义。)在第一次尝试反射和IL之后，我已经能够创建我的dataRow，用值填充它，填充BindingList并在网格中显示结果。当对数据进行更改时，我现在正在尝试实现INotifyPropertyChanged接口和PropertyChangedEventHandler。使用这作为指导，我获得了运行的代码，但似乎没有显示RaisePropertyChanged事件正在触发，或者它只是什么也不做。当我通过ildasm.exe将我的动态版本与普通/静态版本进行比较时，我看到了remove_PropertyChanged和add_PropertyChanged方法的主要区别。有人能提供一些通过反射实现INotifyPropertyChanged接口的技巧或示例吗？

经过进一步的检查，事件字段似乎必须为null，因此不会调用PropertyChangedEventHandler。我在RaiseProprtyChanged方法构建器中添加了一些消息框，发现等效的if (PropertyChanged != null)返回0/false，所以什么都不会发生。如果将OpCodes.Brtrue更改为OpCodes.Brfalse，则会收到“对象引用未设置为对象实例”的消息。感觉好像我错过了一些简单的东西，但我找不到。

            //implement IINotifyPropertyChanged interface
        tb.AddInterfaceImplementation(typeof(INotifyPropertyChanged));

        //property changed event handler
        FieldBuilder eventField = tb.DefineField("PropertyChanged", typeof(PropertyChangedEventHandler), FieldAttributes.Private);

        EventBuilder eb = tb.DefineEvent("PropertyChanged", EventAttributes.None, typeof(PropertyChangedEventHandler));

        MethodBuilder mbEV = tb.DefineMethod("remove_PropertyChanged", MethodAttributes.Public |
            MethodAttributes.SpecialName | MethodAttributes.NewSlot |
            MethodAttributes.HideBySig | MethodAttributes.Virtual |
            MethodAttributes.Final, null, new[] { typeof(PropertyChangedEventHandler) });

        MethodImplAttributes eventMethodFlags = MethodImplAttributes.Managed; //| MethodImplAttributes.Synchronized;
        mbEV.SetImplementationFlags(eventMethodFlags);
        il = mbEV.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldfld, eventField);
        il.Emit(OpCodes.Ldarg_1);
        il.EmitCall(OpCodes.Call, typeof(Delegate).GetMethod("Remove", new[] { typeof(Delegate), typeof(Delegate) }), null);
        il.Emit(OpCodes.Castclass, typeof(PropertyChangedEventHandler));
        il.Emit(OpCodes.Stfld, eventField);
        il.Emit(OpCodes.Ret);
        MethodInfo miRemoveEvent = typeof(INotifyPropertyChanged).GetMethod("remove_PropertyChanged");
        tb.DefineMethodOverride(mbEV, miRemoveEvent);
        eb.SetRemoveOnMethod(mbEV);

        mbEV = tb.DefineMethod("add_PropertyChanged", MethodAttributes.Public |
            MethodAttributes.SpecialName | MethodAttributes.NewSlot |
            MethodAttributes.HideBySig | MethodAttributes.Virtual |
            MethodAttributes.Final, null, new[] { typeof(PropertyChangedEventHandler) });

        mbEV.SetImplementationFlags(eventMethodFlags);
        il = mbEV.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldfld, eventField);
        il.Emit(OpCodes.Ldarg_1);
        il.EmitCall(OpCodes.Call, typeof(Delegate).GetMethod("Combine", new[] { typeof(Delegate), typeof(Delegate) }), null);
        il.Emit(OpCodes.Castclass, typeof(PropertyChangedEventHandler));
        il.Emit(OpCodes.Stfld, eventField);
        il.Emit(OpCodes.Ret);
        MethodInfo miAddEvent = typeof(INotifyPropertyChanged).GetMethod("add_PropertyChanged");
        tb.DefineMethodOverride(mbEV, miAddEvent);
        eb.SetAddOnMethod(mbEV);

        MethodInfo msgboxMethodInfo = typeof(System.Windows.Forms.MessageBox).GetMethod("Show", BindingFlags.Public | BindingFlags.Static, null, CallingConventions.Standard, new Type[] { typeof(String) }, null);

        MethodBuilder mbRaisePropertyChanged = tb.DefineMethod("RaisePropertyChanged", MethodAttributes.Virtual, null, new Type[] { typeof(string) });
        il = mbRaisePropertyChanged.GetILGenerator();
        System.Reflection.Emit.Label labelExit = il.DefineLabel();
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldfld, eventField);
        il.Emit(OpCodes.Ldnull);
        il.Emit(OpCodes.Ceq); //this is returning false
        il.Emit(OpCodes.Brtrue, labelExit);
        il.Emit(OpCodes.Nop); //I never get here
        il.Emit(OpCodes.Ldstr, "After If");
        il.EmitCall(OpCodes.Call, msgboxMethodInfo, null);
        il.Emit(OpCodes.Pop);
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldfld, eventField);
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldarg_1);
        il.Emit(OpCodes.Newobj, typeof(PropertyChangedEventArgs).GetConstructor(new[] { typeof(string) }));
        il.EmitCall(OpCodes.Callvirt, typeof(PropertyChangedEventHandler).GetMethod("Invoke"), null);
        il.Emit(OpCodes.Nop);
        il.Emit(OpCodes.Nop);
        il.MarkLabel(labelExit);
        il.Emit(OpCodes.Ret);

Answer 1

如果您试图修改程序集的IL，我将盗用以避免反射。您可能会遇到程序集锁定问题。

至于解决方案，请尝试这些链接。

定制编织

• NotifyPropertyWeaver
• http://justinangel.net/AutomagicallyImplementingINotifyPropertyChanged

使用后锐器

• http://www.lesnikowski.com/blog/index.php/inotifypropertychanged-with-postsharp/
• http://www.sharpcrafters.com/solutions/ui