Please see my comment to the question.
You are messing up two different things: event invocation and just a method call. You have a method used to handle the event, so you can always call it.
This is already a solution to your "problem".
But now, it sounds a bad UI design idea. Also, you should understand that you can only invoke an event from the class declaring corresponding event member, nowhere else, not even from a derived class. So, you cannot invoke the event directly in the methods of any other types. This is an important fool-proof feature of .NET. (Of course, the declaring type can expose some methods invoking the event indirectly.)
You can handle events more conveniently, which includes the possibility to get the same effect as the event handling by calling a method, if you use
anonymous methods. For example, you are not really using the event arguments parameters, so the handling can be easier:
this.gridSigortaFirmalari.CommandCellClick += (sender, eventArgs) =>
{
HandleCommandCellClick();
}
—SA