NullReferenceException when triggering event

Question

Consider the following:

class Client {     public static event EventHandler connectFailed;      private Socket socket;      public Client()     {         socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);         IPEndPoint endpoint = new IPEndpoint(             IPAddress.Parse("192.168.1.100"),             7900             );          try         {             socket.Connect(endpoint);         }         catch(Exception e)         {             connectFailed(e, new EventArgs());         }     } } 

Assume the rest of the code is implemented (Event handlers and such in Program.cs).

I am running into an issue with NullRefrerenceException on the connectFailed(e, new EventArgs()); line, and I can't understand why. All my other events are firing just fine, and I don't see how this is any different.

Any ideas?

Answer 1

You need a null check - in C# you can't call events when there are no handlers registered on that event.

The normal thing would be to implement an OnConnectFailed method:

protected virtual void OnConnectFailed(e as EventArgs) {     EventHandler tmp = connectFailed;     if(tmp != null)         tmp(this,e); } 

Also, the first argument to the event handler should be this, not the exception. If you need to pass the exception to the event handler, create an EventArgs class with an exception property.

Also, there's no point in raising an event from the constructor... nothing has a chance to add a handler to it.