Associate File Extension with Application

Question

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.

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.

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(); } 

Any idea why it doesn't work? An example use might be

SetAssociation(".ucs", "UCS_Editor_File", Application.ExecutablePath, "UCS File");  

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.

Answer 1

The answer was a lot simpler than I expected. Windows Explorer has its own override for the open with application, and I was trying to modify it in the last lines of code. If you just delete the Explorer override, then the file association will work.

I also told explorer that I had changed a file association by calling the unmanaged function SHChangeNotify() using P/Invoke

public static void SetAssociation(string Extension, string KeyName, string OpenWith, string FileDescription) {     // The stuff that was above here is basically the same      // Delete the key instead of trying to change it     var CurrentUser = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\FileExts\\" + Extension, true);     CurrentUser.DeleteSubKey("UserChoice", false);     CurrentUser.Close();      // Tell explorer the file association has been changed     SHChangeNotify(0x08000000, 0x0000, IntPtr.Zero, IntPtr.Zero); }  [DllImport("shell32.dll", CharSet = CharSet.Auto, SetLastError = true)] public static extern void SHChangeNotify(uint wEventId, uint uFlags, IntPtr dwItem1, IntPtr dwItem2);