How do I assign an event handler to an event in C++/CLI?

Question

How do I add "events" to an "event"/delegate? What is the syntax? Is it the same in C++/CLI and in C#?

Solution 1

In c#, you do it with the += operator:

someObj.SomeEvent += new EventHandler(Blah_SomeEvent);

...

private void Blah_SomeEvent(object sender, EventArgs e)
{
}

More-than-a-year-later-edit

It has been a long time since I posted this answer and someone noticed me that maybe it was wrong. I really don't know why the OP marked my answer as the right one (maybe OP was looking for this rather than c++-cli syntax? Who knows now).

Anyway, in c++-cli it would be:

someObj->SomeEvent+= gcnew EventHandler(this, &Blah_SomeEvent);

Solution 2

1: If underlyng delgate of the event is a custom one you define yourself that is a class memeber (example from MSDN):

delegate void Del(int, float);
ref class EventReceiver {
public:
    void Handler(int i , float f) {  }
};
myEventSource->MyEvent += gcnew Del(myEventReceiver, &EventReceiver::Handler);

2: If the underlying delegate is a global handler and has the standard signature for .NET events (object + event args) (from DPD answer):

delegate void MyOwnEventHandler(Object^ sender, EventArgs^ e) { }  
myEventSource->MyEvent += gcnew EventHandler(MyOwnEventHandler);  

3: If the underlying delegate has the standard signature for .NET events and the event handler is a class method:

ref class EventReceiver {
public:
   void Handler(Object^ sender, EventArgs^ e) {  }
};
myEventSource->MyEvent += gcnew EventHandler(myEventReceiver, &EventReceiver::Handler);

4: Using System::EventHandler generic (that takes a MyEventArgs args parameter) as the underlying delegate:

ref class EventReceiver {
public:
   void Handler(Object^ sender, MyEventArgs^ e) {  }
};
myEventSource->MyEvent += gcnew EventHandler<MyEventArgs^>(this, &EventReceiver::DataReceived);

Solution 3

The syntax for C++/CLI is :

delegate void MyOwnEventHandler(Object^ sender, Eventargs^ e)
{

}

to register this for an event:

objectPtr->MyEvent += gcnew EventHandler(MyOwnEventHandler);

Comments

[Jaroslav Jandek]

Adding events means creating new events. Adding event handlers means subscribing to events so when an event is fired, your assigned handler methods get executed.

[PostMan]

Oh, I find the answers to simple questions are just an important. Helps when the next user searches for the same thing :)

[Matías Fidemraizer]

Right, we avoid redundancy. But you forgot that most RTFM users won't search before asking haha ;)

[dacap]

This is not a correct answer if we look at the question title (C++/CLI is not C#).

[Matías Fidemraizer]

@dacap Maybe you should downvote the question. If I'm wrong that OP looked for C# syntax, it should be that the question was incorrectly asked. Who knows why OP checked my answer as the correct one. Anyway, it seems that the OP found it useful.