Create a notify method to fire the PropertyChanged event.

CreateNotificationMethodDefinition.cs

private MethodDefinition CreateNotificationMethodDefinition()
{
  const string MethodName = "NotifyViewableProperty";
  var methodDef = new MethodDefinition(MethodName,
    MethodAttributes.Private |
    MethodAttributes.HideBySig,
    this._types.Void);
  var paramDef = new ParameterDefinition("propertyName", 
    ParameterAttributes.None, 
    _types.String);
  methodDef.Parameters.Add(paramDef);
  methodDef.Body.MaxStackSize = 4;
  var v = new VariableDefinition(_types.PropertyChangedEventHandler);
  methodDef.Body.Variables.Add(v);
  methodDef.Body.InitLocals = true;

  var il = methodDef.Body.GetILProcessor();
  Action<OpCode> op = x => il.Append(il.Create(x));
  // IL_0000: ldarg.0
  op(OpCodes.Ldarg_0);
  // IL_0001: ldfld class [System]System.ComponentModel.PropertyChangedEventHandler Voodoo.ViewModel.GoalViewModel::PropertyChanged
  var eventHandlerFieldDef = FindEventFieldDeclaration(_typeDef);
  il.Append(il.Create(OpCodes.Ldfld, eventHandlerFieldDef));
  // IL_0006: stloc.0
  op(OpCodes.Stloc_0);
  // IL_0007: ldloc.0
  op(OpCodes.Ldloc_0);
  //IL_0008: brfalse.s IL_0017
  var jumpTargetInsn = il.Create(OpCodes.Ret); // See below, IL_0017
  il.Append(il.Create(OpCodes.Brfalse_S, jumpTargetInsn));
  // IL_000a: ldloc.0
  op(OpCodes.Ldloc_0);
  // IL_000b: ldarg.0
  op(OpCodes.Ldarg_0);
  // IL_000c: ldarg.1
  op(OpCodes.Ldarg_1);
  // IL_000d: newobj instance void [System]System.ComponentModel.PropertyChangedEventArgs::.ctor(string)
  var eventArgsTypeRef = _types.PropertyChangedEventArgs;
  var ctorRef = new MethodReference(".ctor", 
    _types.Void, 
    eventArgsTypeRef);
  var ctorParamDef = new ParameterDefinition("propertyName", 
    ParameterAttributes.None, 
    _types.String);
  ctorRef.Parameters.Add(ctorParamDef);
  ctorRef.HasThis = true;
  il.Append(il.Create(OpCodes.Newobj, ctorRef));
  // IL_0012: callvirt instance void [System]System.ComponentModel.PropertyChangedEventHandler::Invoke(object, class [System]System.ComponentModel.PropertyChangedEventArgs)
  var invokeMethodRef = new MethodReference("Invoke", 
    _types.Void, 
    _types.PropertyChangedEventHandler);
  invokeMethodRef.Parameters.Add(
    new ParameterDefinition(_types.Object));
  invokeMethodRef.Parameters.Add(
    new ParameterDefinition(eventArgsTypeRef));
  invokeMethodRef.HasThis = true;
  il.Append(il.Create(OpCodes.Callvirt, invokeMethodRef));
  // IL_0017: ret
  il.Append(jumpTargetInsn);
  return methodDef;
}