ASP.NET fails to detect Internet Explorer

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