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Assigning File Types to ClickOnce Applications


ClickOnce is a deployment technology used primarily for WinForms based applications. It supports automatic updates and can be launched from either a website or the Start menu. When using the former, query string arguments in the URL are passed to the application.

Using a technique described by Mike Wade, file types can also be associated with ClickOnce applications. This is done by adding a file association tag to the applications manifest file. For Visual Studio users, this means adding an app.manifest file, which will be automatically merged into the full manifest when publishing.

Mike Wade lists a number of rules that must be followed,

  • Values must be given for all 4 xml attributes
  • File associations only work for pure ClickOnce applications. That means that browser-hosted applications and Office documents can't take advantage
  • The application must be targeting the 3.5 version of the .NET Framework
  • The application must be full trust
  • The application must be installed (not run from web)
  • There is a limit of 8 file associations per application

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