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What's wrong with Registry.GetValue?

Asked 2011-03-10T16:39:46.673
9

I trying to get a registry value:

var value = Registry.GetValue(@"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography", "MachineGuid", 0);

In Windows XP all ok, but in Windows 7 returns 0. In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography using regedit I see MachineGuid, but if I run 

var keys = Registry.LocalMachine.OpenSubKey("SOFTWARE").OpenSubKey("Microsoft").OpenSubKey("Cryptography", RegistryKeyPermissionCheck.ReadSubTree).GetValueNames();

keys.Length is 0.

What do I do wrong? With other values all ok in both of OS.

c# .net registry
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2 Answers

7

You say you're on 64-bit Windows: is your app 32-bit? If so it's probably being affected by registry redirection and is looking at HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Cryptography. You may have to P/Invoke to work around it: http://msdn.microsoft.com/en-us/library/aa384129.aspx.

answered 2011-03-10T17:03:54.130
3

If you're not an administrator, you only have read permission on HKLM. You need to open the key read-only instead. Not sure how to do that with .NET's Registry class; with the API directly, you use RegOpenKeyEx() with the KEY_READ flag.

EDIT: After checking MSDN, I see that OpenSubKey() does open read only, and returns the contents if it succeeds and nothing if it fails. Since you're chaining multiple OpenSubKey calls, it's most likely one of them that's failing that causes the others to fail. Try breaking them out into separate calls, and checking the intermediate values returned.

answered 2011-03-10T16:48:42.543

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