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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. 		if (self.GetType() == type)
  13.                 return self;
  14.  
  15. 		return Delegate.Combine(
  16. 			self.GetInvocationList()
  17. 				.Select(i => Delegate.CreateDelegate(type, i.Target, i.Method))
  18. 				.ToArray());
  19. 	}
  20.  
  21. 	public static T ConvertTo<T>(this Delegate self)
  22. 	{
  23. 		return (T)(object)self.ConvertTo(typeof(T));
  24. 	}
  25. }
  26.  
  27. public class A  { }
  28.  
  29. public class B : A {}
  30.  
  31. public delegate void MyEventHandler<in T>(object sender, T arg);
  32.  
  33. public class TheClass {
  34.  
  35.  	public event MyEventHandler<B> MyEvent {
  36.  		add {
  37.  			this._myEvent += value.ConvertTo<MyEventHandler<B>>();
  38.  		}
  39.  		remove {
  40.  			this._myEvent -= value.ConvertTo<MyEventHandler<B>>();
  41.  		}
  42.  	}
  43.  
  44. 	private MyEventHandler<B> _myEvent; 
  45.  
  46. 	public void RaiseEvent(B arg)
  47. 	{
  48. 		var handler = this._myEvent;
  49. 		if(handler != null)
  50. 			handler(this, arg);
  51. 	}
  52.  
  53. }
  54.  
  55. class Program
  56. {
  57. 	static void Main()
  58. 	{
  59. 		var obj = new TheClass();
  60.  
  61. 		obj.MyEvent += new MyEventHandler<B>((sender, e) => Console.WriteLine("B handler: Hey there from {0} with {1}!", sender, e));
  62. 		obj.MyEvent += new MyEventHandler<A>((sender, e) => Console.WriteLine("A handler: Hey there from {0} with {1}!", sender, e));
  63. 		obj.MyEvent += new MyEventHandler<object>((sender, e) => Console.WriteLine("Object handler: Hey there from {0} with {1}!", sender, e));
  64.  
  65. 		obj.RaiseEvent(new B());
  66. 	}
  67. }
Success #stdin #stdout 0.05s 24344KB
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B handler: Hey there from TheClass with B!
A handler: Hey there from TheClass with B!
Object handler: Hey there from TheClass with B!
https://ideone.com/O6YcdI
language:
C# (gmcs 5.20.1)
created:
8 years ago
visibility:
secret

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