title: ClickOnce Upgrade Fails after Converting to .NET 4
body: <p>Our application is .NET 3.5 deployed via ClickOnce.  We just upgrade to .NET 4.0 and updated the pre-requisities appropriately.</p>
  
  <p>The install still works fine for first-time users or users who install via the setup HTML page. It will automatically install the .NET 4 framework for them. However, users who already have the application installed and attempt to run it via the start menu get the prompt:</p>
  
  <p>"Unable to install or run this application. This application requires your system to be updated to the Microsoft Common Language Runtime Version 4.0.30319.0. More information can be found here" (link to MS website)</p>
  
  <p>Why doesn't it automatically install .NET 4.0 as it does when you run it from the html page? It does not even give the option to download updates. We need a seamless solution for our customers to upgrade to the new application without re-installing manually.</p>