In C#, why can't I test if a event handler is null anywhere outside of the class that it's defined?

Question

I am sure that I am just not understanding something fundamental about events and/or delegates in C#, but why can\'t I do the Boolean tests in this code sample:

Answer 1

You can easily use a very simple approach here to not repeatedly subscribe to an event.

Either of the 2 approaches below can be used:

1. Flag approach : _getWarehouseForVendorCompletedSubscribed is a private variable initialized to false.

       if (!_getWarehouseForVendorCompletedSubscribed)
       {
           _serviceClient.GetWarehouseForVendorCompleted += new EventHandler<GetWarehouseForVendorCompletedEventArgs>(_serviceClient_GetWarehouseForVendorCompleted);
           _getWarehouseForVendorCompletedSubscribed = true;
       }
   

2. Unsubscribe Approach :Include an unsubscribe everytime you want to subscribe.

   _serviceClient.GetWarehouseForVendorCompleted -= new 
       EventHandler<GetWarehouseForVendorCompletedEventArgs>  
    (_serviceClient_GetWarehouseForVendorCompleted);
   
   
   _serviceClient.GetWarehouseForVendorCompleted += new 
          EventHandler<GetWarehouseForVendorCompletedEventArgs>
          (_serviceClient_GetWarehouseForVendorCompleted);