Clicking "X" on the ASP.NET popup event

I'm stuck with the question, simple at f开发者_开发知识库irst glance

Which event raises when we close ASP.NET popup window by clicking "x" in the top right corner?

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If you mean WinForms event, it would be Form_Closing followed by Form_Closed. In Asp.Net there's no event that can be caught on the server directly, since this is a client side event. However, you CAN, in client side script, catch this event (onUnload or onbeforeunload) and trigger a postback to the server if you need to.