What is the use of object sender and EventArgs e parameters

Question

In case of Page Load  Init and other page events  what is the use of these  object sender  EventArgs e  parameters   Examples would be more helpful

User · Accepted Answer

EventArgs e is a parameter called e that contains the event data  see the EventArgs MSDN page for more information   Object Sender is a parameter called Sender that contains a reference to the control object that raised the event   Event Arg Class  http   msdn microsoft com en-us library system eventargs aspx  Example   protected void btn Click  object sender  EventArgs e      Button btn   sender as Button     btn Text    clicked        Edit  When Button is clicked  the btn Click event handler will be fired  The  object sender  portion will be a reference to the button which was clicked

User · Answer

Those two parameters  or variants of  are sent  by convention  with all events    sender  The object which has raised the event e an instance of EventArgs including  in many cases  an object which inherits from EventArgs  Contains additional information about the event  and sometimes provides ability for code handling the event to alter the event somehow    In the case of the events you mentioned  neither parameter is particularly useful  The is only ever one page raising the events  and the EventArgs are Empty as there is no further information about the event   Looking at the 2 parameters separately  here are some examples where they are useful   sender  Say you have multiple buttons on a form  These buttons could contain a Tag describing what clicking them should do  You could handle all the Click events with the same handler  and depending on the sender do something different  private void HandleButtonClick object sender  EventArgs e        Button btn    Button sender      if btn Tag     Hello         MessageBox Show  Hello       else if btn Tag     Goodbye          Application Exit           etc      Disclaimer   That s a contrived example  don t do that   e  Some events are cancelable  They send CancelEventArgs instead of EventArgs  This object adds a simple boolean property Cancel on the event args  Code handling this event can cancel the event   private void HandleCancellableEvent object sender  CancelEventArgs e        if    some condition                    Cancel this event        e Cancel   true

[c#] What is the use of "object sender" and "EventArgs e" parameters?

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