Registry.LocalMachine.OpenSubKey() returns null

Question

I get a null back from this attempt to access the Windows Registry:

using (RegistryKey registry = Registry.LocalMachine.OpenSubKey(keyPath))

keyPath is SOFTWARE\\TestKey

The key is in the registry, so why is it not finding it under the Local Machine hive?

Answer 1

It can happen if you are on a 64-bit machine. Create a helper class first (requires .NET 4.0 or later):

public class RegistryHelpers
{

    public static RegistryKey GetRegistryKey()
    {
        return GetRegistryKey(null);
    }

    public static RegistryKey GetRegistryKey(string keyPath)
    {
        RegistryKey localMachineRegistry
            = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine,
                                      Environment.Is64BitOperatingSystem
                                          ? RegistryView.Registry64
                                          : RegistryView.Registry32);

        return string.IsNullOrEmpty(keyPath)
            ? localMachineRegistry
            : localMachineRegistry.OpenSubKey(keyPath);
    }

    public static object GetRegistryValue(string keyPath, string keyName)
    {
        RegistryKey registry = GetRegistryKey(keyPath);
        return registry.GetValue(keyName);
    }
}

Usage:

string keyPath = @"SOFTWARE\MyApp\Settings";
string keyName = "MyAppConnectionStringKey";

object connectionString = RegistryHelpers.GetRegistryValue(keyPath, keyName);

Console.WriteLine(connectionString);
Console.ReadLine();

Answer 2

In your comment to Dana you said you gave the ASP.NET account access. However, did you verify that that is the account that the site in running under? Impersonate and the anonymous access user can be easy to overlook.

UNTESTED CODE:

Response.Clear();  
Response.Write(Environment.UserDomainName + "\\" + Environment.UserName);  
Response.End();

Answer 3

Just needed to change it from

using (RegistryKey registry = Registry.LocalMachine.OpenSubKey(keyPath))

to

using (RegistryKey registry = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Default).OpenSubKey(keyPath))

(Use RegistryKey instead of Registry , add the RegistryView, and put the hive-Local Machine as a method parameter.)