How to get Windows user name from SessionID?

Question

Is there a method in C# to retrieve the user name from a given session id?
(any session running on the system)

The Win API function WTSQuerySessionInformation does this, but I'm searching for this functionality in C#.

Answer 1

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;
    }