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Implementing INotifyPropertyChanged with Reflection.Emit

Using C # /. NET 4.0, I store the data in a BindingList, where the dataRow is determined at runtime through Reflection.Emit. (The structure of the input data is changed and determined by an external source.) After a battle with my first foray into the world of reflection and IL, I was able to create my dataRow, fill it with values, fill my BindingList and display the result in the grid. Now I'm trying to implement the INotifyPropertyChanged and PropertyChangedEventHandler interface when data changes are made. using thisas a guide, I have some code that works, but it doesn't seem that the RaisePropertyChanged event is fired, or it just isn’t doing anything. When I compare my dynamic version with the normal / static version using ildasm.exe, I see significant differences in the remove_PropertyChanged and add_PropertyChanged methods Can anyone provide some tips or examples of implementing the INotifyPropertyChanged interface through reflection.

After further viewing, it seems that the event field should be null, so PropertyChangedEventHandler will not be called. I added some message boxes in the RaiseProprtyChanged method builder, and I found that the equivalent of if (PropertyChanged! = Null) returns zero / false, so nothing happens. If I changed OpCodes.Brtrue to OpCodes.Brfalse, I get the message "Link to an object that is not installed on an object instance." It seems to me that I will miss something simple, but I can not find it.

            //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);
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1 answer

If you are trying to change the assembly IL, I would get rid of the reflection. You may encounter build lock issues.

, .

postsharp

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