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c#registry

Access to registry seems to be different from different sources

I am trying to add a registry key in my C# code under

HKEY_CLASSES_ROOT\*\shell\blabla

I want the user to be able to send any file to my application, kind of like Open with UltraEdit or so.

I don't have administrator rights and the users won't have administrator privileges, too.

  1. If I am doing that in my C# code as posted below, I get a

    System.UnauthorizedAccessException

    Registry.SetValue("HKEY_CLASSES_ROOT\\*\\shell\\blabla", null, "FastSearch");
string path = Application.ExecutablePath;
Registry.SetValue("HKEY_CLASSES_ROOT\\*\\shell\\blabla" + "\\Command", null, path + " \"%1\"");

  2. If I run Regedit and attempt to do it manually myself, I get a similar error:

    Error! Key could not be created. Error when writing to the registry.

BUT, if I double click a *.reg file that attempts to write the SAME KEY, everything works!

So why is that?

And do I have a chance to get this done through code?
Or should I just change my code to run that *.reg file?

UPDATE:

Actually the *.reg file did not write the SAME KEY as stated above, but

HKEY_CURRENT_USER\Software\Classes\*\shell\blabla

I didn't notice that. It seems as anything added under HKEY_CURRENT_USER\Software\Classes*\shell\blabla is also added to HKEY_CLASSES_ROOT\*\shell\blabla. Sorry for the confusion.

Solution

  • Although the problem is solved already and the reason for successful import of *.reg file was found out also in the meantime in comparison to C# code, here is a complete answer for this question.

    HKEY_CLASSES_ROOT Key (short HKCR) as described by Microsoft shows file name extension associations and COM class registration information which are effective for the current user.

    The real locations in registry for those keys are:

    • HKEY_LOCAL_MACHINE\Software\Classes (short HKLM\Software\Classes) containing the defaults for all users using a machine and

    • HKEY_CURRENT_USER\Software\Classes (short HKCU\Software\Classes) containing the user specific settings which override the default settings from HKLM\Software\Classes.

    A registry write to HKEY_CLASSES_ROOT is always redirected to HKLM\Software\Classes. A write access to any key in HKLM requires administrative privileges which is the reason for the error message.

    Microsoft recommends to write directly to either HKLM\Software\Classes or to HKCU\Software\Classes depending on changing the defaults or the effective file associations for the current user.

    Write operations to keys under HKCU do not require administrative privileges.

    HKCR should be used only for reading currently effective settings for file name extension associations and COM class registration information and not for adding or changing them.