C# – Launching GUI App from Windows Service – Window Does Not Appear

c++windowswindows-services

I have written a simple windows service which will launch a exe specified in the
onstart() method of the service. After starting the service the exe got launched it only
presents in the memory but it doesnt show in the explorer.

I'm trying to launch a calc.exe from my code.it shows the exe in the memory but it
doesnt comes into my view(i.e) in the explorer.

Below is my code to launch the exe in the onStart() method

    Process pr=new Process();
    pr.StartInfo.FileName="calc.exe";
    pr.StartInfo.WindowStyle=ProcessWindowStyle.Maximized;
    pr.StartInfo.CreateNoWindow=false;
    pr.Start();
//  pr.WaitForExit();

Best Solution

Services run in other session on Vista or later and applications started directly from services are started in the same session by default. Starting applications in other sessions is possible - you have to find the id of the user session and use CreateProcessAsUser.

If more than one user is logged in and you need to start your program for all users you must find the ids of all sessions.

Here is sample code:

int session = Win32.WTSGetActiveConsoleSessionId();
if (session == 0xFFFFFFFF)
{
    return false;
}

IntPtr userToken;
bool res = Win32.WTSQueryUserToken(session, out userToken);
if (!res)
{
    this.log.WriteEntry("Error WTSQueryUserToken");
    return false;
}

string path = GetPath();
string dir = Path.GetDirectoryName(path);
Win32.STARTUPINFO si = new Win32.STARTUPINFO();
si.lpDesktop = "winsta0\\default";
si.cb = Marshal.SizeOf(si);

Win32.PROCESS_INFORMATION pi = new Win32.PROCESS_INFORMATION();
Win32.SECURITY_ATTRIBUTES sa = new Win32.SECURITY_ATTRIBUTES();
sa.bInheritHandle = 0;
sa.nLength = Marshal.SizeOf(sa);
sa.lpSecurityDescriptor = IntPtr.Zero;

if (!Win32.CreateProcessAsUser(userToken,       // user token
                                path,           // exexutable path
                                string.Empty,   // arguments
                                ref sa,         // process security attributes ( none )
                                ref sa,         // thread  security attributes ( none )
                                false,          // inherit handles?
                                0,              // creation flags
                                IntPtr.Zero,    // environment variables
                                dir,            // current directory of the new process
                                ref si,         // startup info
                                out pi))        // receive process information in pi
{
    int error = Marshal.GetLastWin32Error();
    this.log.WriteEntry("Error CreateProcessAsUser:" + error);
    return false;
}
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