RtlGetVersion

C# Signature:

[DllImport("ntdll.dll", SetLastError=true)]
static extern int RtlGetVersion(ref OSVERSIONINFOEXW versionInfo);

Boo Signature:

[DllImport("ntdll.dll", SetLastError : true)]
def RtlGetVersion(ref versionInfo as OSVERSIONINFOEXW) as bool:
     pass

User-Defined Types:

enum PRODUCT_TYPE:
     VER_NT_WORKSTATION = 0x0000001
     VER_NT_DOMAIN_CONTROLLER = 0x0000002
     VER_NT_SERVER = 0x0000003

[StructLayout(LayoutKind.Sequential, CharSet : CharSet.Unicode)]
struct OSVERSIONINFOEXW:
     dwOSVersionInfoSize as int
     dwMajorVersion as int
     dwMinorVersion as int
     dwBuildNumber as int
     dwPlatformId as int
     [MarshalAs(UnmanagedType.ByValTStr, SizeConst : 128)]
     szCSDVersion as string
     wServicePackMajor as UInt16
     wServicePackMinor as UInt16
     wSuiteMask as UInt16
     wProductType as PRODUCT_TYPE
     wReserved as byte

Sample Code:

var osvi = default(OSVERSIONINFOEXW);
        osvi.dwOSVersionInfoSize = Marshal.SizeOf(typeof(OSVERSIONINFOEXW));
        var result = RtlGetVersion(ref osvi);
        if (result != 0)
        {
           // TODO: Error handling
        }
        else
        {
           return osvi;
        }