How to detect Windows 64-bit platform with .NET?

Question

In a .NET 2.0 C# application I use the following code to detect the operating system platform:

string os_platform = System.Environment.OSVersion.Platform.ToString();

This returns "Win32NT". The problem is that it returns "Win32NT" even when running on Windows Vista 64-bit.

Is there any other method to know the correct platform (32 or 64 bit)?

Note that it should also detect 64 bit when run as a 32 bit application on Windows 64 bit.

Answer 1

If you're using .NET Framework 4.0, it's easy:

Environment.Is64BitOperatingSystem

See Environment.Is64BitOperatingSystem Property (MSDN).

Answer 2

Use these two environment variables (pseudo code):

if (PROCESSOR_ARCHITECTURE = x86 &&
    isDefined(PROCESSOR_ARCHITEW6432) &&
    PROCESSOR_ARCHITEW6432 = AMD64) {

    //64 bit OS
}
else
    if (PROCESSOR_ARCHITECTURE = AMD64) {
        //64 bit OS
    }
    else
        if (PROCESSOR_ARCHITECTURE = x86) {
            //32 bit OS
        }

Refer to the blog post HOWTO: Detect Process Bitness.

Answer 3

Here is the direct approach in C# using DllImport from this page.

[DllImport("kernel32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)] 
[return: MarshalAs(UnmanagedType.Bool)] 
public static extern bool IsWow64Process([In] IntPtr hProcess, [Out] out bool lpSystemInfo); 

public static bool Is64Bit() 
{ 
    bool retVal; 

    IsWow64Process(Process.GetCurrentProcess().Handle, out retVal); 

    return retVal; 
} 

Answer 4

I found this to be the best way to check for the platform of the system and the process:

bool 64BitSystem = Environment.Is64BitOperatingSystem;
bool 64BitProcess = Environment.Is64BitProcess;

The first property returns true for 64-bit system, and false for 32-bit. The second property returns true for 64-bit process, and false for 32-bit.

The need for these two properties is because you can run 32-bit processes on 64-bit system, so you will need to check for both the system and the process.

Answer 5

IntPtr.Size won't return the correct value if running in 32-bit .NET Framework 2.0 on 64-bit Windows (it would return 32-bit).

As Microsoft's Raymond Chen describes, you have to first check if running in a 64-bit process (I think in .NET you can do so by checking IntPtr.Size), and if you are running in a 32-bit process, you still have to call the Win API function IsWow64Process. If this returns true, you are running in a 32-bit process on 64-bit Windows.

Microsoft's Raymond Chen: How to detect programmatically whether you are running on 64-bit Windows

My solution:

static bool is64BitProcess = (IntPtr.Size == 8);
static bool is64BitOperatingSystem = is64BitProcess || InternalCheckIsWow64();

[DllImport("kernel32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool IsWow64Process(
    [In] IntPtr hProcess,
    [Out] out bool wow64Process
);

public static bool InternalCheckIsWow64()
{
    if ((Environment.OSVersion.Version.Major == 5 && Environment.OSVersion.Version.Minor >= 1) ||
        Environment.OSVersion.Version.Major >= 6)
    {
        using (Process p = Process.GetCurrentProcess())
        {
            bool retVal;
            if (!IsWow64Process(p.Handle, out retVal))
            {
                return false;
            }
            return retVal;
        }
    }
    else
    {
        return false;
    }
}

Answer 6

Enjoy ;-)

Function Is64Bit() As Boolean

    Return My.Computer.FileSystem.SpecialDirectories.ProgramFiles.Contains("Program Files (x86)")

End Function