Why Visual Studio Controls Event functions written, but it still gives error?

i was working in asp.net, suddenly i found that, the buttons and controls lost the code behind, like if i place a button and click on it, and as it automatically writes functions but it still gives error 'ASP.meeting_schedular_aspx' d开发者_StackOverflowoes not contain a definition for 'Button1_Click1' and no extension method 'Button1_Click1' accepting a first argument of type 'ASP.meeting_schedular_aspx' could be found (are you missing a using directive or an assembly reference?)

Even there is definition of this function available in csharp file.

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This error usually occurs when you hide the contents of master pages with manual css code, like we do styling display:none to the default master pages content.