title: Associate File Extension with Application
body: <p>I've written a program that edits a specific filetype , and I want to give the user the option to set my application as the default editor for this filetype (since I don't want an installer) on startup.</p>
  
  <p>I've tried to write a re-useable method that associates a file for me (preferably on any OS, although I'm running Vista) by adding a key to HKEY_CLASSES_ROOT, and am using it with my application, but it doesn't seem to work.</p>
  
  <pre><code>public static void SetAssociation(string Extension, string KeyName, string OpenWith, string FileDescription)
  {
      RegistryKey BaseKey;
      RegistryKey OpenMethod;
      RegistryKey Shell;
      RegistryKey CurrentUser;
  
      BaseKey = Registry.ClassesRoot.CreateSubKey(Extension);
      BaseKey.SetValue("", KeyName);
  
      OpenMethod = Registry.ClassesRoot.CreateSubKey(KeyName);
      OpenMethod.SetValue("", FileDescription);
      OpenMethod.CreateSubKey("DefaultIcon").SetValue("", "\"" + OpenWith + "\",0");
      Shell = OpenMethod.CreateSubKey("Shell");
      Shell.CreateSubKey("edit").CreateSubKey("command").SetValue("", "\"" + OpenWith + "\"" + " \"%1\"");
      Shell.CreateSubKey("open").CreateSubKey("command").SetValue("", "\"" + OpenWith + "\"" + " \"%1\"");
      BaseKey.Close();
      OpenMethod.Close();
      Shell.Close();
  
      CurrentUser = Registry.CurrentUser.CreateSubKey(@"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\" + Extension);
      CurrentUser = CurrentUser.OpenSubKey("UserChoice", RegistryKeyPermissionCheck.ReadWriteSubTree, System.Security.AccessControl.RegistryRights.FullControl);
      CurrentUser.SetValue("Progid", KeyName, RegistryValueKind.String);
      CurrentUser.Close();
  }
  </code></pre>
  
  <p>Any idea why it doesn't work? An example use might be </p>
  
  <pre><code>SetAssociation(".ucs", "UCS_Editor_File", Application.ExecutablePath, "UCS File"); 
  </code></pre>
  
  <p>The part of the method that uses "CurrentUser" seems to work if I do the same using regedit, but using my application it doesn't.</p>