ASP.NET fails to detect Internet Explorer

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Certain versions of ASP.NET do not correctly recognize the latest version of Windows Internet Explorer and must be updated.

When ASP.NET does not correctly recognize Internet Explorer, it responds with a "_doPostBack is undefined JavaScript" error.

To resolve this issue, do one of the following:

  • Revise the application to use feature detection, rather than browser detection (preferred).
  • Update the ASP.NET browser definition files.

Internet Explorer compatibility cookbook

How to detect features instead of browsers

Detecting Internet Explorer more effectively