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Raise and handle events generically

/ Published in: C#
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For a discussion of .NET events best-practices, see [Roy Osherove's blog post](http://weblogs.asp.net/rosherove/articles/DefensiveEventPublishing.aspx) and [this post](http://blogs.msdn.com/ericlippert/archive/2009/04/29/events-and-races.aspx). Be sure to read the comments sections for some good arguments for and against the presented methods. Also, there is a good [MSDN Magazine article on Event Accessors](http://msdn.microsoft.com/en-us/magazine/cc163533.aspx), which may be useful.

Used in "Empire." The example shows an EventArgs with a DateTime object, but it could be a string or enumeration or whatever.

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  1. /// <summary>
  2. /// Generic EventArgs class to hold event data.
  3. /// </summary>
  4. /// <example>
  5. /// To create an event that sends a string (such as an error message):
  6. /// <code>
  7. /// public event EventHandler{EventArgs{string}} EventOccurred;
  8. /// EventOccurred.Raise(sender, "The event occurred");
  9. /// </code>
  10. /// </example>
  11. /// <see cref="http://geekswithblogs.net/HouseOfBilz/archive/2009/02/15/re-thinking-c-events.aspx"/>
  12. /// <typeparam name="T">Any data</typeparam>
  13. public class EventArgs<T> : EventArgs
  14. {
  15.     public T Args { get; private set; }
  16.     public EventArgs(T args)
  17.     {
  18.         Args = args;
  19.     }
  20.     public override string ToString()
  21.     {
  22.         return Args.ToString();
  23.     }
  24. }
  25.     /// <summary>
  26.     /// Tell subscribers, if any, that this event has been raised.
  27.     /// </summary>
  28.     /// <typeparam name="T"></typeparam>
  29.     /// <param name="handler">The generic event handler</param>
  30.     /// <param name="sender">this or null, usually</param>
  31.     /// <param name="args">Whatever you want sent</param>
  32.     public static void Raise<T>(this EventHandler<EventArgs<T>> handler, object sender, T args)
  33.     {
  34.         // Copy to temp var to be thread-safe (taken from C# 3.0 Cookbook - don't know if it's true)
  35.         EventHandler<EventArgs<T>> copy = handler;
  36.         if (copy != null)
  37.         {
  38.             copy(sender, new EventArgs<T>(args));
  39.         }
  40.     }
  41.  
  42. class Tester
  43. {
  44.     public static event EventHandler<EventArgs<DateTime>> GetTime_Rcvd;
  45.  
  46.     static void Main()
  47.     {
  48.         GetTime_Rcvd.Raise(null, MyDateTime);
  49.     }
  50. }

URL: http://geekswithblogs.net/HouseOfBilz/archive/2009/02/15/re-thinking-c-events.aspx

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