How read the 64 bit registry from a 32 bit application or vice versa

I found out that I needed to read the 64 bit registry from a 32 bit app today.
Why you might ask?
Well, I need to get the RegisteredOrganization value from HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion and unfortunately Microsoft has a bug where the WOW6432 version of this key always says Microsoft, so a 32 bit application would always return Microsoft as the RegisteredOrganization, regardless of what the user entered when they installed the OS. This is hardly desired.
Note: This is also why all Visual Studio projects created in Windows 7 64 bit have Microsoft in the project’s Assembly Information. Change the WOW6432 version of the RegisteredOrganization and you fix this Visual Studio issue.
Well, turns out C# doesn’t have functionality until .NET 4, so prior to .NET 4, to choose the 64 bit hive when running a 32 bit app, so we have to do use a DLLImport and use RegOpenKeyEx, RegCloseKey, and RegQueryValueEx.
I don’t have this well commented, and it is not very newbie proof, but here are three different ways to do this. Hopefully you can understand one or more of these.

Example 1 – .NET 4 Example

Here is how to do this in .NET 4.
using Microsoft.Win32;

namespace Read64bitRegistryFrom32bitApp
{
    class Program
    {
        static void Main(string[] args)
        {
            string value64 = string.Empty;
            string value32 = string.Empty;

            RegistryKey localKey = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry64);
            localKey = localKey.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion");
            if (localKey != null)
            {
                value64 = localKey.GetValue("RegisteredOrganization").ToString();
            }
            RegistryKey localKey32 = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry32);
            localKey32 = localKey32.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion");
            if (localKey32 != null)
            {
                value32 = localKey32.GetValue("RegisteredOrganization").ToString();
            }
        }
    }
}

.NET 3.5 SP1 and Prior

This can also be done in .NET 3.5 and prior but it is not easy.
We have to do use a DLLImport and use RegOpenKeyEx, RegCloseKey, and RegQueryValueEx. Here are some examples.

Example 1 – A console application to read the 64 bit registry from a 32 bit application or vice versa

Here is the code in a simple one file project:
using System;
using System.Runtime.InteropServices;
using System.Text;

namespace Read64bitRegistryFrom32bitApp
{
    class Program
    {
        static void Main(string[] args)
        {
            string value64 = GetRegKey64(RegHive.HKEY_LOCAL_MACHINE, @"SOFTWARE\Microsoft\Windows NT\CurrentVersion", "RegisteredOrganization");
            Console.WriteLine(value64);
            string value32 = GetRegKey32(RegHive.HKEY_LOCAL_MACHINE, @"SOFTWARE\Microsoft\Windows NT\CurrentVersion", "RegisteredOrganization");
            Console.WriteLine(value32);
        }

        public 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
        }

        public static UIntPtr HKEY_LOCAL_MACHINE = new UIntPtr(0x80000002u);
        public static UIntPtr HKEY_CURRENT_USER = new UIntPtr(0x80000001u);

        #region Member Variables
        #region Read 64bit Reg from 32bit app
        [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);
        #endregion
        #endregion

        #region Functions
        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
    }
}

Example 2 – A static class to read the 64 bit registry from a 32 bit application or vice versa

Or if you want this in its own separate class, here is a static class you can add to your project.
using System;
using System.Runtime.InteropServices;
using System.Text;

namespace Read64bitRegistryFrom32bitApp
{
    public 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
    }

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

    public static class RegistryWOW6432
    {
        #region Member Variables
        #region Read 64bit Reg from 32bit app
        [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);
        #endregion
        #endregion

        #region Functions
        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

        #region Enums
        #endregion
    }
}
Here is an example of using this class.
using System;
using System.Runtime.InteropServices;
using System.Text;

namespace Read64bitRegistryFrom32bitApp
{
    class Program
    {
        static void Main(string[] args)
        {
            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");
        }
    }
}

Example 3 – Adding extension methods to the managed RegistryKey object that read the 64 bit registry from a 32 bit application or vice versa

You know what else is a cool idea? Making it an extension class to the normal managed registry C# code. So you can create a regular managed RegistryKey and then just call an extension function off it.
using System;
using System.Runtime.InteropServices;
using System.Text;
using Microsoft.Win32;

namespace Read64bitRegistryFrom32bitApp
{
    /// <summary>
    /// An extension class to allow a registry key to allow it to get the
    /// registry in the 32 bit (Wow6432Node) or 64 bit regular registry key
    /// </summary>
    public static class RegistryWOW6432
    {
        #region Member Variables
        #region Read 64bit Reg from 32bit app
        public static UIntPtr HKEY_LOCAL_MACHINE = new UIntPtr(0x80000002u);
        public static UIntPtr HKEY_CURRENT_USER = new UIntPtr(0x80000001u);

        [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);
        #endregion
        #endregion

        #region Functions
        public static string GetRegKey64(this RegistryKey inKey, String inPropertyName)
        {
            string strKey = inKey.ToString();
            string regHive = strKey.Split('\\')[0];
            string regPath = strKey.Substring(strKey.IndexOf('\\') +1);
            return GetRegKey64(GetRegHiveFromString(regHive), regPath, RegSAM.WOW64_64Key, inPropertyName);
        }

        public static string GetRegKey32(this RegistryKey inKey, String inPropertyName)
        {
            string strKey = inKey.ToString();
            string regHive = strKey.Split('\\')[0];
            string regPath = strKey.Substring(strKey.IndexOf('\\') + 1);
            return GetRegKey64(GetRegHiveFromString(regHive), regPath, RegSAM.WOW64_32Key, inPropertyName);
        }

        private static UIntPtr GetRegHiveFromString(string inString)
        {
            if (inString == "HKEY_LOCAL_MACHINE")
                return HKEY_LOCAL_MACHINE;
            if (inString == "HKEY_CURRENT_USER")
                return HKEY_CURRENT_USER;
            return UIntPtr.Zero;
        }

        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(inHive, 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

        #region Enums
        public 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
        }
        #endregion
    }
}
Here is an example of using these extension functions.
using System;
using System.Runtime.InteropServices;
using System.Text;
using Microsoft.Win32;

namespace Read64bitRegistryFrom32bitApp
{
    class Program
    {
        static void Main(string[] args)
        {
            string value64 = string.Empty;
            string value32 = string.Empty;
            RegistryKey localKey = Registry.LocalMachine;
            localKey = localKey.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion");
            if (localKey != null)
            {
                value32 = localKey.GetRegKey32("RegisteredOrganization");
                value64 = localKey.GetRegKey64("RegisteredOrganization");
            }
        }
    }
}
If anything is confusing please comment.
Resources:
  • RegOpenKeyEx Function – http://msdn.microsoft.com/en-us/library/ms724897%28v=VS.85%29.aspx
  • RegQueryValueEx Function – http://msdn.microsoft.com/en-us/library/ms724911%28VS.85%29.aspx
  • http://www.pinvoke.net/default.aspx/advapi32/RegQueryValueEx.html
  • http://www.pinvoke.net/default.aspx/advapi32/RegOpenKeyEx.html
  • http://www.pinvoke.net/default.aspx/advapi32/RegCreateKeyEx.html
  • http://www.pinvoke.net/default.aspx/advapi32/RegCloseKey.html
  • http://stackoverflow.com/questions/1470770/accessing-registry-using-net
  • http://connect.microsoft.com/VisualStudio/feedback/details/400597/registeredorganization-reg-key-on-x64-vista-7

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8 Comments

  1. Marcel G. says:

    Example 2 was exactly what I needed for my program, thanks.
    The only possibility to make it better, would be to make a method for “writing” into the registry. So I could use something like:
    if(GetRegKey32(…)==NULL)
    SetRegKey32(…)

  2. Mohan says:

    Rhyous! Thanks for the code. I have been searching for an example like your example 1. You saved my time.

  3. Chris Motter says:

    In example #2 your last GetRegKey64() method accepts a parameter called inHive but this is not used in the method; in fact it’s hard-coded to only allow LOCAL_MACHINE. It appears that it’s just a leftover from debugging and that it should actually make use of the RegHive class above.

    At first glance I’m guessing that you can just remove the hard-coded reference and replace it with the inHive parameter to fix this.

  4. Matt says:

    A bit help to get me started thanks

  5. Marcin says:

    Nice, helped me a lot. Thanks!

  6. Sparky says:

    In example 3, lines 41 and 49 include the this keyword. Is it necessary to include those? Thanks.

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