.NET Events - What are object sender & EventArgs e?

.net events event-handling
stringo0 picture stringo0 · Aug 20, 2009 · Viewed 184.9k times · Source

What do sender and eventArgs mean/refer to? How can I make use of them (for the scenario below)?

Scenario:

I'm trying to build a custom control with a delete function, and I want to be able to delete the control that was clicked on a page that contains many of the same custom control.

Answer

Noon Silk picture Noon Silk · Aug 20, 2009

The sender is the control that the action is for (say OnClick, it's the button).

The EventArgs are arguments that the implementor of this event may find useful. With OnClick it contains nothing good, but in some events, like say in a GridView 'SelectedIndexChanged', it will contain the new index, or some other useful data.

What Chris is saying is you can do this:

protected void someButton_Click (object sender, EventArgs ea)
{
    Button someButton = sender as Button;
    if(someButton != null)
    {
        someButton.Text = "I was clicked!";
    }
}

Related questions

Understanding events and event handlers in C#

I understand the purpose of events, especially within the context of creating user interfaces. I think this is the prototype for creating an event: public void EventName(object sender, EventArgs e); What do event handlers do, why are they needed, …

Read More
Should I always disconnect event handlers in the Dispose method?

I'm working in C# and my workplace has some code standards. One of them is that each event handler we connect (such as KeyDown) must be disconnected in the Dispose method. Is there any good reason for that?

Read More
Raising C# events with an extension method - is it bad?

We're all familiar with the horror that is C# event declaration. To ensure thread-safety, the standard is to write something like this: public event EventHandler SomethingHappened; protected virtual void OnSomethingHappened(EventArgs e) { var handler = SomethingHappened; if (handler != null) handler(this, …

Read More