How to get Windows user name from SessionID?

There seems to be no .NET integrated method for this.
So this is the current solution, using Windows Terminal services API:

    [DllImport("Wtsapi32.dll")]    private static extern bool WTSQuerySessionInformation(IntPtr hServer, int sessionId, WtsInfoClass wtsInfoClass, out System.IntPtr ppBuffer, out int pBytesReturned);    [DllImport("Wtsapi32.dll")]    private static extern void WTSFreeMemory(IntPtr pointer);    public enum WtsInfoClass    {        WTSInitialProgram,        WTSApplicationName,        WTSWorkingDirectory,        WTSOEMId,        WTSSessionId,        WTSUserName,        WTSWinStationName,        WTSDomainName,        WTSConnectState,        WTSClientBuildNumber,        WTSClientName,        WTSClientDirectory,        WTSClientProductId,        WTSClientHardwareId,        WTSClientAddress,        WTSClientDisplay,        WTSClientProtocolType,        WTSIdleTime,        WTSLogonTime,        WTSIncomingBytes,        WTSOutgoingBytes,        WTSIncomingFrames,        WTSOutgoingFrames,        WTSClientInfo,        WTSSessionInfo,    }    public static string GetUsernameBySessionId(int sessionId, bool prependDomain) {        IntPtr buffer;        int strLen;        string username = "SYSTEM";        if (WTSQuerySessionInformation(IntPtr.Zero, sessionId, WtsInfoClass.WTSUserName, out buffer, out strLen) && strLen > 1) {            username = Marshal.PtrToStringAnsi(buffer);            WTSFreeMemory(buffer);            if (prependDomain) {                if (WTSQuerySessionInformation(IntPtr.Zero, sessionId, WtsInfoClass.WTSDomainName, out buffer, out strLen) && strLen > 1) {                    username = Marshal.PtrToStringAnsi(buffer) + "\\" + username;                    WTSFreeMemory(buffer);                }            }        }        return username;    }