OpenSubKey() returns null for a registry key that I can see in regedit.exe

Question

I'm trying to get all the display names of the sub keys within this key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

With this code:

     RegistryKey newKey;
     string val;

     string KeyPath64Bit = @"SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall";
     RegistryKey mainKey = Registry.LocalMachine.OpenSubKey(KeyPath64Bit);

     string[] RegKeys64Bits = Registry.LocalMachine.OpenSubKey(KeyPath64Bit).GetSubKeyNames();

     foreach (string s in RegKeys64Bits)
     {
        newKey = mainKey.OpenSubKey(s);
        val = newKey.GetValue("DisplayName", -1, RegistryValueOptions.None).ToString();
        if (val != "-1")
           file64.WriteLine(val);
     }

After running the code I can't find one of the keys I need:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{DA5E371C-6333-3D8A-93A4-6FD5B20BCC6E}

And it should have the display name: Microsoft Visual C++ 2010 x64 Redistributable - 10.0.30319, but instead the GetSubKeyNames() method gives me the sub key : {DA5E371C-6333-3D8A-93A4-6FD5B20BCC6E}.KB2151757 which doesn't have any display name.

Why can't I get the exact sub key I need ({DA5E371C-6333-3D8A-93A4-6FD5B20BCC6E}) and how can I get it?

Inexpungible

Answer 1

A 32-bit application on a 64-bit OS will be looking at the HKLM\Software\Wow6432Node node by default. To read the 64-bit version of the key, you'll need to specify the RegistryView:

using (var hklm = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64))
using (var key = hklm.OpenSubKey(@"SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall"))
{
   // key now points to the 64-bit key
}

The API to do this was added in .NET 4.0; if you're still using 3.5, you'll need to use P/Invoke to access the 64-bit keys: http://www.rhyous.com/2011/01/24/how-read-the-64-bit-registry-from-a-32-bit-application-or-vice-versa/

Radmen

Thanks for this. Although I still don't understand why there are two registries. – Utopia

@RobertNoack: I think it's mainly for COM, and to ensure that environment variables get expanded correctly in REG_EXPAND_SZ values. There's some information on MSDN - Registry Redirector – Radmen

You saved my day. I was getting freaked out with the way registry key was behaving for me. +1. – Ibbetson

I must have read a dozen explainers; this is the first to show the RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64)) step. Thanks!! – Boylan

I run with Debug\x64 dotnet 4.6.1, but problem still exists. I can read the same path in another C# project with the same code. – Misconduct

Answer 2

In Visual Studio 2017 go to

Project > Properties > Build > Uncheck **Prefer 32-bit** and Platform target as **Any CPU**.

Caporetto

I had the same issue - I unchecked 32Bit and it worked fine. – Schiro