How to force Visual Studio to regenerate the .designer file

Solution 1:

Check html view header if CodeBehind existed

 CodeBehind="~/Your.aspx.cs"

Solution 2:

Reformat or modify html view and check if anything syntax problem for html tags

Solution 3:

   1. Delete the designer.cs file from your project

   2. Rightclick your main aspx file and select “Convert to Web Application“.

Reference:

http://stackoverflow.com/questions/45325/how-do-you-force-visual-studio-to-regenerate-the-designer-files-for-aspx-ascx-fi