title: Need to detect if .NET 4.5 is installed using useragent
body: <p>In order to run  our WPF xbap application,  we need to make sure our clients machines have .NET 4.5 on them. There was a big bug fix in 4.5 that corrected a threading bug that was in the 4.0 E version.</p>
  
  <p>we are doing a check for the client versions using javascript.</p>
  
  <p>With 4.5 RC installed, the useragent string is still reporting just 4.0E. We need to be able to tell if 4.5 is installed so if it is we can let the user run the app without getting the notice to update. Can this be done? Will 4.5 create the proper string for the useragent call?</p>
  
  <p>Thanks
  Harold</p>