To add the form size change and pre-exit confirmation function in C # winform, you must add the resize and formclosing events on your own.

To add the form size change and pre-exit confirmation function in C # winform, add the resize and formclosing events on your own. The method is as follows:
 
Add the following in initializecomponent () of frmmain. Designer. CS:
This. Resize + = new system. eventhandler (this. frmmain_resize );
This. formclosing + = new system. Windows. Forms. formclosingeventhandler (this. frmmain_formclosing );
 
Add the following in frmmain. CS:
Private void frmmain_resize (Object sender, eventargs E)
{
This. Text = "...";
}
Private void frmmain_formclosing (Object sender, formclosingeventargs E)
{
If (MessageBox. Show ("are you sure you want to exit? "," System prompt ", messageboxbuttons. yesno, messageboxicon. Information, messageboxdefaultbutton. button1) = dialogresult. Yes)
E. Cancel = false;
Else
E. Cancel = true;
}