Reading the registry and Wow6432Node key

I have some code that reads the registry and looks for a value in HKEY_LOCAL_MACHINE\Software\App\ but when running on 64-bit versions of Windows the value is under HKEY_LOCAL_MACHINE\Software\Wow6432Node\App\.

How should I best approach this? Do I need a 64-bit installer or should I rewrite my code to detect both places?

Solution 1:

On an x64 machine, here is an example of how to access the 32-bit view of the registry:

using (var view32 = RegistryKey.OpenBaseKey(RegistryHive.CurrentUser,
                                            RegistryView.Registry32))
{
  using (var clsid32 = view32.OpenSubKey(@"Software\Classes\CLSID\", false))
  {
    // actually accessing Wow6432Node 
  }
}

... as compared to...

using (var view64 = RegistryKey.OpenBaseKey(RegistryHive.CurrentUser,
                                            RegistryView.Registry64))
{
  using (var clsid64 = view64.OpenSubKey(@"Software\Classes\CLSID\", true))
  {
    ....
  }
}

Solution 2:

If you mark you C# program as x86 (and not Any CPU) then it will see HKEY_LOCAL_MACHINE\Software\Wow6432Node\App as HKEY_LOCAL_MACHINE\Software\App\.

A .NET program for Any CPU will run as a 64-bit process if 64-bit .NET is installed. The 32-bit registry is under the Wow6432Node for 64-bit programs.

Solution 3:

+1 to Wally's answer, but his solution works for .NET 4.0 and higher.

I've found another solution, which also works for .NET 2.0 here

#region RegHelper
enum RegSAM
{
    QueryValue = 0x0001,
    SetValue = 0x0002,
    CreateSubKey = 0x0004,
    EnumerateSubKeys = 0x0008,
    Notify = 0x0010,
    CreateLink = 0x0020,
    WOW64_32Key = 0x0200,
    WOW64_64Key = 0x0100,
    WOW64_Res = 0x0300,
    Read = 0x00020019,
    Write = 0x00020006,
    Execute = 0x00020019,
    AllAccess = 0x000f003f
}

static class RegHive
{
    public static UIntPtr HKEY_LOCAL_MACHINE = new UIntPtr(0x80000002u);
    public static UIntPtr HKEY_CURRENT_USER = new UIntPtr(0x80000001u);
}

static class RegistryWOW6432
{
    [DllImport("Advapi32.dll")]
    static extern uint RegOpenKeyEx(UIntPtr hKey, string lpSubKey, uint ulOptions, int samDesired, out int phkResult);

    [DllImport("Advapi32.dll")]
    static extern uint RegCloseKey(int hKey);

    [DllImport("advapi32.dll", EntryPoint = "RegQueryValueEx")]
    public static extern int RegQueryValueEx(int hKey, string lpValueName, int lpReserved, ref uint lpType, System.Text.StringBuilder lpData, ref uint lpcbData);

    static public string GetRegKey64(UIntPtr inHive, String inKeyName, string inPropertyName)
    {
        return GetRegKey64(inHive, inKeyName, RegSAM.WOW64_64Key, inPropertyName);
    }

    static public string GetRegKey32(UIntPtr inHive, String inKeyName, string inPropertyName)
    {
        return GetRegKey64(inHive, inKeyName, RegSAM.WOW64_32Key, inPropertyName);
    }

    static public string GetRegKey64(UIntPtr inHive, String inKeyName, RegSAM in32or64key, string inPropertyName)
    {
        //UIntPtr HKEY_LOCAL_MACHINE = (UIntPtr)0x80000002;
        int hkey = 0;

        try
        {
            uint lResult = RegOpenKeyEx(RegHive.HKEY_LOCAL_MACHINE, inKeyName, 0, (int)RegSAM.QueryValue | (int)in32or64key, out hkey);
            if (0 != lResult) return null;
            uint lpType = 0;
            uint lpcbData = 1024;
            StringBuilder AgeBuffer = new StringBuilder(1024);
            RegQueryValueEx(hkey, inPropertyName, 0, ref lpType, AgeBuffer, ref lpcbData);
            string Age = AgeBuffer.ToString();
            return Age;
        }
        finally
        {
            if (0 != hkey) RegCloseKey(hkey);
        }
    }
}
#endregion

Usage:

string value64 = RegistryWOW6432.GetRegKey64(RegHive.HKEY_LOCAL_MACHINE, @"SOFTWARE\Microsoft\Windows NT\CurrentVersion", "RegisteredOrganization");
string value32 = RegistryWOW6432.GetRegKey32(RegHive.HKEY_LOCAL_MACHINE, @"SOFTWARE\Microsoft\Windows NT\CurrentVersion", "RegisteredOrganization");