Trace the browser window close button click

Hi all,

I have to trace the browser window close button click event, is there any way to do that.

I have a problem that I have to call a logout function if someone closes the window by clicking on the close button of browser window. If I am using the logout function on the Page_Unload event then every time the page loses control this function will be called which I don't want. I only want that the user will get logout if he clicks on the close button or alt+F4 is pressed, is there any way that could help me.

Thanks a lot in advance.
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