Attaching an event handler multiple times

If you keep attaching event handlers then it will be raised once for each time you've attached the handler. This means:

• If you only need it to be raised once then assign one handler.
• If you attach the same handler 4 times then it will be called 4 times.

Looking at your code, instead of hooking into the CurrentCellActivated event multiple times it would make more sense to subscribe to a general CellActivated event once.

You can prevent it by unsubscribing before adding it,

Object.Event -= EventHandler(method);
Object.Event += EventHandler(method);

if can be done, prevent it by always subscribe events in one place say constructor

Try it yourself:

static class Program
{
    static event EventHandler MyEvent;

    static void Main()
    {
        // registering event
        MyEvent += Program_MyEvent;
        MyEvent += Program_MyEvent;
        MyEvent += Program_MyEvent;
        MyEvent += Program_MyEvent;
        MyEvent += Program_MyEvent;

        // invoke event
        MyEvent(null, EventArgs.Empty);
        Console.ReadKey();
    }

    static void Program_MyEvent(object sender, EventArgs e)
    {
        Console.WriteLine("MyEvent fired");
    }
}

Output:

MyEvent fired
MyEvent fired
MyEvent fired
MyEvent fired
MyEvent fired