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

.NET 4 has two new properties in the Environment class, Is64BitProcess and Is64BitOperatingSystem. Interestingly, if you use Reflector you can see they are implemented differently in the 32-bit & 64-bit versions of mscorlib. The 32-bit version returns false for Is64BitProcess and calls IsWow64Process via P/Invoke for Is64BitOperatingSystem. The 64-bit version just returns true for both.

Answer 2

UPDATE: As Joel Coehoorn and others suggest, starting at .NET Framework 4.0, you can just check Environment.Is64BitOperatingSystem.

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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;     } }