How to open a WOW64 registry key from a 64-bit .NET application

Question

My .NET application (any-CPU) needs to read a registry value created by a 32-bit program. On 64-bit Windows this goes under the Wow6432Node key in the registry. I have read that you shouldn't hard-code to the Wow6432Node, so what's the right way to access it with .NET?

Answer 1

In the case where you explicitly need to read a value written by a 32 bit program in a 64 bit program, it's OK to hard code it. Simply because there really is no other option.

I would of course abstract it out to a helper function. For example

public RegistryKey GetSoftwareRoot() {
  var path = 8 == IntPtr.Size 
    ? @"Software\Wow6432Node"
    : @"Software";
  return Registry.CurrentUser.OpenSubKey(path);
}

Answer 2

If you can change the target .Net version to v4, then you can use the new OpenBaseKey function e.g.

RegistryKey registryKey;
if (Environment.Is64BitOperatingSystem == true)
{
    registryKey = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry64);
}
else
{
    registryKey = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry32);
}

Answer 3

The correct way would be to call the native registry api and passing the KEY_WOW64_32KEY flag to RegOpenKeyEx/RegCreateKeyEx

Answer 4

Extending Anders's answer, there's a good example of wrapping the resulting handle in a .NET RegistryKey object on Shahar Prish's blog - be sure to read the comments too though.

Note that unvarnished use of the pinvoke.net wrapper of RegOpenKeyEx is fraught with issues.