Question

Is it possible to create a custom attribute (MyAttribute) such that during run-time the get of Derived.MyProperty actually calls Base.GetProperty(“MyProperty”) and the set of Derived.MyProperty calls Base.SetProperty(“MyProperty”, value).

class Derived : Base
{
  [MyAttribute]
  string MyProperty { get; set;}
}

class Base
{
  XmlDoc _xmldoc;
  void SetProperty(string key, string value)
  {
    set key, value into _xmldoc;
  }
  string GetProperty(string key);
  {
    get key value from _xmldoc;
  }
}

Here is the solution derived from the comments below. Thanks to all commenters.

public class WatchAttribute : HandlerAttribute
{
  public override ICallHandler CreateHandler(IUnityContainer container)
  {
    return new WatchHandler();
  }
}

public class WatchHandler : ICallHandler
{
  public int Order { get; set; }
  public IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext)
  {
    Console.WriteLine(string.Format("Method '{0}' on object '{1}' was invoked.", 
    return getNext()(input, getNext);
  }
}

public class SomeAction : MarshalByRefObject
{
  [Watch]
  public string MyProperty1 { get; set; }

  public string MyProperty { get; set; }
}

class Program
{
  static void Main(string[] args)
  {
    SomeAction c = new SomeAction();
    IUnityContainer container = new UnityContainer()
      .AddNewExtension<Interception>();
    container.Configure<Interception>()
      .SetInterceptorFor<SomeAction>(new TransparentProxyInterceptor())
      .AddPolicy("WatchAttribute Policy")
      .AddMatchingRule(new PropertyMatchingRule("*", PropertyMatchingOption.GetOrSet));
    container.RegisterInstance<SomeAction>(c);
    c = container.Resolve<SomeAction>();

    c.MyProperty1 = "Hello";
    c.MyProperty = "Hello";
  }
}

Answer 1

use unity interception it will be better because it allow you to have a proxy that wrap you method you want and specify rule to filter method
here an explanation:
http://www.lm-tech.it/Blog/post/2011/10/18/How-to-use-the-Unity-Interception-Extension.aspx
it allow you to make your process without setting any attribute and your developper will have only to follow a rule name for example (all properties that work with your xmldoc is prefixed with Xml_…