Why is OpenSubKey() returning null on my Windows 7 64-bit system?

Question

Do OpenSubKey() and other Microsoft.Win32 registry functions return null on 64-bit systems when 32-bit registry keys are under Wow6432node in the registry?

I'm working on a unit testing framework that makes a call to OpenSubKey() from the .NET library.

My development system is a Windows 7 64-bit environment with Visual Studio 2008 SP1 and the Windows 7 SDK installed.

The application we're unit testing is a 32-bit application, so the registry is virtualized under HKLM\Software\Wow6432node. When we call:

Registry.LocalMachine.OpenSubKey( @"Software\MyCompany\MyApp\" );

Null is returned, however explicitly stating to look here works:

Registry.LocalMachine.OpenSubKey( @"Software\Wow6432node\MyCompany\MyApp\" );

From what I understand this function should be agnostic to 32-bit or 64-bit environments and should know to jump to the virtual node.

Even stranger is the fact that the exact same call inside a compiled and installed version of our application is running just fine on the same system and is getting the registry keys necessary to run; which are also being placed in HKLM\Software\Wow6432node.

What should I do?

Answer 1

It sounds like your unit testing project compiles to 64 bit. In the Compile settings of your unit testing project, set the "Target CPU" to x86 (instead of AnyCPU).

Answer 2

If you really need a 32 bit application, you can access the 64 bit registry like this:

RegistryKey localMachine64 = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry64);
RegistryKey regKey = localMachine64.OpenSubKey(@"Software\MyCompany\MyApp\", false);

Answer 3

Yes, I also have the same issue with Windows 7 64-bit and Visual Studio 2008 SP1. But my solution is the opposite, which is to change from "x86" to either "Any CPU" or "x64".