EventsHelper delegate trigger class

• When using events, we often write the following: public event EventHandler ChangedEvent;
  Private void OnChangedEvent ()
  {
  If (ChangedEvent! = Null)
  {
  ChangedEvent (this, EventArgs. Empty );
  }
  }
  Private void OnChangeEventAsync ()
  {
  If (ChangedEvent! = Null)
  {
  ChangedEvent. BeginInvoke (this, EventArgs. Empty, null, null );
  }
  }
• Judging whether an event has a subscription or trigger event is a frequently repeated part. In fact, we can encapsulate it.

1. To create an EventsHelper static class, first complete the synchronization operation: create the following method: // Private check Parameter Function
   Private static bool CheckArguments (Delegate del, params object [] args)
   {
   If (del = null) {return false ;}
   If (args. Length> 7)
   {
   Throw new ArgumentOutOfRangeException ("too many parameters ");
   }
   Return true;
   }
   // Delegate trigger function
   Private static void Fire (Delegate del, params object [] args)
   {
   Foreach (var item in del. GetInvocationList ())
   {
   Try
   {
   Item. DynamicInvoke (args );
   }
   Catch {}
   }
   }
   // Non-type security delegate trigger function
   Public static void UnsafeFire (Delegate del, params object [] args)
   {
   If (CheckArguments (del, args ))
   {
   Fire (del, args );
   }
   }
2. Since the UnsafeFire () method does not check the parameter type, the type security cannot be ensured. Therefore, we create some common