I'm having problem with Team Foundation Server (TFS) when viewing .cs files and need to delete the file association with .cs in Windows 7. At the moment I go to Control Panel -> Default Programs trying to do this, but it seems to have no way to delete other than change the current association. So, how can I do it?


1 Answer 1

  1. Open an elevated command prompt with administrator privileges.

  2. Remove the file extension association from its assigned file. Type in the following command and press Enter:

    assoc .ext=

    Replace .ext with the extension name that needs to be disassociated. For example, to disassociate WinRAR's .rar extension, simply type: assoc .rar =

    Note that after disassociation of a file extension from file type, the default program for the file type will no longer be shown in the "Open With" list for the file extension.

  3. Clear and delete the default program used for the Open command when launching files of this type. Enter the following command and press Enter:

    ftype FileType=

    Replace "FileType" with the actual name for the file type associated to the file extension to be removed from the system. For example, for WinRAR, type ftype WinRAR=

    Note that if you don't know the correct "FileType", simply type assoc (associated file type will be shown after the extension) or ftype to get a listing of all file types defined in the system.

  • Would you suggest what command I should use with .cs (C#) files for the two command?
    – Nam G VU
    Commented Jul 4, 2010 at 17:12
  • 3
    when i execute the #2 step, "File association not found for extension .xxx" appears.. but when i look in Default Programs > Set Associations, the .xxx file has its current default association. i'm a bit confused... what did i missed out? 0_0
    – CMA
    Commented Apr 2, 2013 at 2:23
  • Thank you for pointing this out. Never heard before, it saved my day!
    – jlandercy
    Commented Nov 8, 2016 at 15:07
  • 6
    @CMA you will also need to change in registry if you changed by Explorer: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.py (see superuser.com/a/49617/185071)
    – Liviu
    Commented Jan 2, 2018 at 13:58
  • 1
    You can filter desired ftypes with a command: ftype | findstr python gives every association containing "python"
    – Rabash
    Commented Apr 11, 2019 at 20:02

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