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  1. using System;
  2. using System.Linq;
  3. using System.Threading;
  4.  
  5. static class Extensions
  6. {
  7. 	public static Delegate ConvertTo(this Delegate self, Type type)
  8. 	{
  9. 		if (type == null) { throw new ArgumentNullException("type"); }
  10. 		if (self == null) { return null; }
  11.  
  12. 		return Delegate.Combine(
  13. 			self.GetInvocationList()
  14. 				.Select(i => Delegate.CreateDelegate(type, i.Target, i.Method))
  15. 				.ToArray());
  16. 	}
  17.  
  18. 	public static T ConvertTo<T>(this Delegate self)
  19. 	{
  20. 		return (T)(object)self.ConvertTo(typeof(T));
  21. 	}
  22. }
  23.  
  24. public class MyEventArgs : EventArgs { }
  25.  
  26. public delegate void MyEventHandler(object sender, MyEventArgs e);
  27.  
  28. public class Foo {
  29.  
  30. public event EventHandler<MyEventArgs> MyEvent;
  31.  
  32. public bool IsEventNull() {
  33. 	return MyEvent == null;
  34. }
  35.  
  36. }
  37.  
  38. public class Bar {
  39. 	public Foo Impl = new Foo();
  40.  
  41. 	public event MyEventHandler MyEvent {
  42. 		add {
  43. 			Impl.MyEvent += value.ConvertTo<EventHandler<MyEventArgs>>();
  44. 		} 
  45. 		remove {
  46. 			Impl.MyEvent -= value.ConvertTo<EventHandler<MyEventArgs>>();
  47. 		}
  48. 	}
  49. }
  50.  
  51. public class Baz {
  52. 	public void MyHandler(object sender, MyEventArgs e) {}
  53. }
  54.  
  55. class Program
  56. {
  57. 	static void Main()
  58. 	{
  59. 		var bar = new Bar();
  60. 		var baz = new Baz();
  61.  
  62. 		Console.WriteLine("event is null: {0}", bar.Impl.IsEventNull());
  63.  
  64. 		bar.MyEvent += baz.MyHandler;
  65.  
  66. 		Console.WriteLine("event is null: {0}", bar.Impl.IsEventNull());
  67.  
  68. 		bar.MyEvent -= baz.MyHandler;
  69.  
  70. 		Console.WriteLine("event is null: {0}", bar.Impl.IsEventNull());
  71. 	}
  72. }
Success #stdin #stdout 0.03s 33696KB
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Standard input is empty
stdout
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event is null: True
event is null: False
event is null: True
https://ideone.com/fBS2PH
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
secret

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