Windows – VBS Windows 64bit/32bit registry read problem

Yes, you can target both x86 and x64 with the same code base in the same project. In general, things will Just Work if you create the right solution configurations in VS.NET (although P/Invoke to entirely unmanaged DLLs will most likely require some conditional code): the items that I found to require special attention are:

• References to outside managed assemblies with the same name but their own specific bitness (this also applies to COM interop assemblies)
• The MSI package (which, as has already been noted, will need to target either x86 or x64)
• Any custom .NET Installer Class-based actions in your MSI package

The assembly reference issue can't be solved entirely within VS.NET, as it will only allow you to add a reference with a given name to a project once. To work around this, edit your project file manually (in VS, right-click your project file in the Solution Explorer, select Unload Project, then right-click again and select Edit). After adding a reference to, say, the x86 version of an assembly, your project file will contain something like:

<Reference Include="Filename, ..., processorArchitecture=x86">
  <HintPath>C:\path\to\x86\DLL</HintPath>
</Reference>

Wrap that Reference tag inside an ItemGroup tag indicating the solution configuration it applies to, e.g:

<ItemGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">
   <Reference ...>....</Reference>
</ItemGroup>

Then, copy and paste the entire ItemGroup tag, and edit it to contain the details of your 64-bit DLL, e.g.:

<ItemGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x64' ">
  <Reference Include="Filename, ..., processorArchitecture=AMD64">
     <HintPath>C:\path\to\x64\DLL</HintPath>
   </Reference>
</ItemGroup>

After reloading your project in VS.NET, the Assembly Reference dialog will be a bit confused by these changes, and you may encounter some warnings about assemblies with the wrong target processor, but all your builds will work just fine.

Solving the MSI issue is up next, and unfortunately this will require a non-VS.NET tool: I prefer Caphyon's Advanced Installer for that purpose, as it pulls off the basic trick involved (create a common MSI, as well as 32-bit and 64-bit specific MSIs, and use an .EXE setup launcher to extract the right version and do the required fixups at runtime) very, very well.

You can probably achieve the same results using other tools or the Windows Installer XML (WiX) toolset, but Advanced Installer makes things so easy (and is quite affordable at that) that I've never really looked at alternatives.

One thing you may still require WiX for though, even when using Advanced Installer, is for your .NET Installer Class custom actions. Although it's trivial to specify certain actions that should only run on certain platforms (using the VersionNT64 and NOT VersionNT64 execution conditions, respectively), the built-in AI custom actions will be executed using the 32-bit Framework, even on 64-bit machines.

This may be fixed in a future release, but for now (or when using a different tool to create your MSIs that has the same issue), you can use WiX 3.0's managed custom action support to create action DLLs with the proper bitness that will be executed using the corresponding Framework.

Edit: as of version 8.1.2, Advanced Installer correctly supports 64-bit custom actions. Since my original answer, its price has increased quite a bit, unfortunately, even though it's still extremely good value when compared to InstallShield and its ilk...

Edit: If your DLLs are registered in the GAC, you can also use the standard reference tags this way (SQLite as an example):

<ItemGroup Condition="'$(Platform)' == 'x86'">
    <Reference Include="System.Data.SQLite, Version=1.0.80.0, Culture=neutral, PublicKeyToken=db937bc2d44ff139, processorArchitecture=x86" />
</ItemGroup>
<ItemGroup Condition="'$(Platform)' == 'x64'">
    <Reference Include="System.Data.SQLite, Version=1.0.80.0, Culture=neutral, PublicKeyToken=db937bc2d44ff139, processorArchitecture=AMD64" />
</ItemGroup>

The condition is also reduced down to all build types, release or debug, and just specifies the processor architecture.

Reading the 64 bit registry is possible because of WOW64 which is a Windows subsystem providing access to 64 bit from within 32 bit applications. (Likewise, in older NT-based Windows versions it was called WOW and was an emulation layer inside 32 bit Windows to support 16 bit applications).

There is still native support for registry access under 64 bit Windows using .NET Framework 4.x and for newer .NET versions (such as .NET Core, .NET 5 and 6) as well. The following code is tested with  Windows 7, 64 bit  and also with  Windows 10, 64 bit.

Instead of using "Wow6432Node", which emulates a node by mapping one registry tree into another making it appear there virtually, you can do the follwing:

Decide, whether you need to access the 64 bit or the 32 bit registry, and use it as described below. You may also use the code I mentioned later (Additional information section), which creates a union query to get registry keys from both nodes in one query - so you can still query them by using their real path.

64 bit registry

To access the 64 bit registry, you can use RegistryView.Registry64 as follows:

// using Microsoft.Win32
string value64 = 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(); 
    localKey.Close();
} 
Console.WriteLine(String.Format("RegisteredOrganization [value64]: {0}",value64));

32 bit registry

If you want to access the 32bit registry, use RegistryView.Registry32 as follows:

// using Microsoft.Win32
string value32 = string.Empty; 
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(); 
    localKey32.Close();
} 
Console.WriteLine(String.Format("RegisteredOrganization [value32]: {0}",value32));

Don't be confused, both versions are using Microsoft.Win32.RegistryHive.LocalMachine as first parameter, you make the distinction whether to use 64 bit or 32 bit by the 2nd parameter (RegistryView.Registry64 versus RegistryView.Registry32).

Note that

• On a 64bit Windows, HKEY_LOCAL_MACHINE\Software\Wow6432Node contains values used by 32 bit applications running on the 64 bit system. Only true 64 bit applications store their values in HKEY_LOCAL_MACHINE\Software directly. The subtree Wow6432Node is entirely transparent for 32 bit applications, 32 bit applications still see HKEY_LOCAL_MACHINE\Software as they expect it (it is a kind of redirection). In older versions of Windows as well as 32 bit Windows 7 (and Vista 32 bit) the subtree Wow6432Node obviously does not exist.

• Due to a bug in Windows 7 (64 bit), the 32 bit source code version always returns "Microsoft" regardless which organization you have registered while the 64 bit source code version returns the right organization.

Coming back to the example you've provided, do it the following way to access the 64 bit branch:

RegistryKey localKey = 
    RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, 
        RegistryView.Registry64); 
RegistryKey sqlServerKey = localKey.OpenSubKey(
    @"SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL");
string sqlExpressKeyName = (string) sqlServerKey.GetValue("SQLEXPRESS");

Additional information - for practical use:

I'd like to add an interesting approach Johny Skovdal has suggested in the comments, which I've picked up to develop some useful functions by using his approach: In some situations you want to get back all keys regardless whether it is 32 bit or 64 bit. The SQL instance names are such an example. You can use a union query in that case as follows (C#6 or higher):

// using Microsoft.Win32;
public static IEnumerable<string> GetRegValueNames(RegistryView view, string regPath,
                                  RegistryHive hive = RegistryHive.LocalMachine) 
{ 
    return RegistryKey.OpenBaseKey(hive, view)
                     ?.OpenSubKey(regPath)?.G‌​etValueNames();
}

public static IEnumerable<string> GetAllRegValueNames(string RegPath,
                                  RegistryHive hive = RegistryHive.LocalMachine) 
{
    var reg64 = GetRegValueNames(RegistryView.Registry64, RegPath, hive);
    var reg32 = GetRegValueNames(RegistryView.Re‌​gistry32, RegPath, hive);
    var result = (reg64 != null && reg32 != null) ? reg64.Union(reg32) : (reg64 ?? reg32);
    return (result ?? new List<string>().AsEnumerable()).OrderBy(x => x);
}

public static object GetRegValue(RegistryView view, string regPath, string ValueName="",
                                 RegistryHive hive = RegistryHive.LocalMachine)
{
    return RegistryKey.OpenBaseKey(hive, view)
                       ?.OpenSubKey(regPath)?.G‌​etValue(ValueName);
}

public static object GetRegValue(string RegPath, string ValueName="",
                                 RegistryHive hive = RegistryHive.LocalMachine)
{   
    return GetRegValue(RegistryView.Registry64, RegPath, ValueName, hive) 
                     ?? GetRegValue(RegistryView.Re‌​gistry32, RegPath, ValueName, hive);
}

public static IEnumerable<string> GetRegKeyNames(RegistryView view, string regPath,
                   RegistryHive hive = RegistryHive.LocalMachine)
{
    return RegistryKey.OpenBaseKey(hive, view)
        ?.OpenSubKey(regPath)?.GetSubKeyNames(); 
}

public static IEnumerable<string> GetAllRegKeyNames(string RegPath,
                                  RegistryHive hive = RegistryHive.LocalMachine)
{
    var reg64 = GetRegKeyNames(RegistryView.Registry64, RegPath, hive);
    var reg32 = GetRegKeyNames(RegistryView.Re‌​gistry32, RegPath, hive);
    var result = (reg64 != null && reg32 != null) ? reg64.Union(reg32) : (reg64 ?? reg32);
    return (result ?? new List<string>().AsEnumerable()).OrderBy(x => x);
}

Now you can simply use the functions above as follows:

Example 1: Get SQL instance names

var sqlRegPath=@"SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL";
foreach (var valueName in GetAllRegValueNames(sqlRegPath))
{
    var value=GetRegValue(sqlRegPath, valueName);
    Console.WriteLine($"{valueName}={value}");
}

will give you a list of the value names and values in sqlRegPath.

Note: You can access the default value of a key (displayed by the commandline tool REGEDT32.EXE as (Default)) if you omit the ValueName parameter in the corresponding functions above.

To get a list of SubKeys within a registry key, use the function GetRegKeyNamesor GetAllRegKeyNames. You can use this list to traverse further keys in the registry.

Example 2: Get uninstall information of installed software

var currentVersionRegPath = @"SOFTWARE\Microsoft\Windows\CurrentVersion";
var uninstallRegPath = $@"{currentVersionRegPath}\Uninstall";
var regKeys = Registry.GetAllRegKeyNames(RegPath: uninstallRegPath);

will get all 32 bit and 64 bit uninstall keys.

Notice the null handling required in the functions because SQL server can be installed as 32 bit or as 64 bit (Example 1 above). The functions are overloaded so you can still pass the 32 bit or 64 bit parameter if required - however, if you omit it then it will try to read 64 bit, if that fails (null value), it reads the 32 bit values.

There is one speciality here: Because GetAllRegValueNames is usually used in a loop context (see Example 1 above), it returns an empty enumerable rather than null to simplify foreach loops: if it wouldn't be handled that way, the loop would have to be prefixed by an if statement checking for null which would be cumbersome having to do that - so that is dealt with once in the function.

Why bothering about null? Because if you don't care, you'll have a lot more headaches finding out why that null reference exception was thrown in your code - you'd spend a lot of time finding out where and why it happened. And if it happened in production you'll be very busy studying log files or event logs (I hope you have logging implemented) ... better avoid null issues where you can in a defensive way. The operators ?., ?[...] and ?? can help you a lot (see the code provided above). There is a nice related article discussing the new nullable reference types in C#, which I recommend to read and also this one about the Elvis operator.

Hint: You can use the free edition of Linqpad to test all examples under Windows. It doesn't require an installation. Don't forget to press F4 and enter Microsoft.Win32 in the Namespace import tab. In Visual Studio, you require using Microsoft.Win32; at the top of your code.

Tip: To familiarize yourself with the new null handling operators, try out (and debug) the following code in LinqPad:

Example 3: Demonstrating null handling operators

static string[] test { get { return null;} } // property used to return null
static void Main()
{
    test.Dump();                    // output: null
    // "elvis" operator:
    test?.Dump();                   // output: 
    // "elvis" operator for arrays
    test?[0].Dump();                // output: 
    (test?[0]).Dump();              // output: null
    // combined with null coalescing operator (brackets required):
    (test?[0]??"<null>").Dump();    // output: "<null>"
}

Try it with .Net fiddle

If you're interested, here are some examples I put together showing what else you can do with the tool.