Starting a process fails in OnStart code block of a service

Question

I only would like to call

Process.Start("notepad.exe");

when the service starts; But it doesn't work at all. No notepad is called right after I chose to start the service in the windows service manager.

Thank you a lot.

[ UPDATE ]

I made it work after putting a check mark in logon tab to allow interactive desktop. But I don't know what does this really mean ? How can I schedule to run a task on any computer if it always asks me to accept to view the message in the Interactive Desktop Detection panel ?

Answer 1

A Windows service is different from a standard process and by default it can't interact with the user desktop(this is a rule of the Windows OS), so to launch a process and allow it to interact with the user desktop you have to flag the Interact with desktop option ...

Bear in mind that starting from Windows Vista services are running under session 0 and every time that the service try to start the process a panel is shown to the user the let the user choose if he wants to run the process or not; to overcome this limitation (panel that ask for confirmation) the only way is to launch the process from the service directly with the CreateProcessAsUser function of the Windows API ...

Take a look at this function that i have developed some times ago, that make use of the CreateProcessAsUser API, and start a process from a service without asking anything even in Vista/7:

    /// <summary>
    /// LaunchProcess As User Overloaded for Window Mode 
    /// </summary>
    /// <param name="cmdLine"></param>
    /// <param name="token"></param>
    /// <param name="envBlock"></param>
    /// <param name="WindowMode"></param>
    /// <returns></returns>
    private static bool LaunchProcessAsUser(string cmdLine, IntPtr token, IntPtr envBlock,uint WindowMode)
    {
        bool result = false;

        PROCESS_INFORMATION pi = new PROCESS_INFORMATION();
        SECURITY_ATTRIBUTES saProcess = new SECURITY_ATTRIBUTES();
        SECURITY_ATTRIBUTES saThread = new SECURITY_ATTRIBUTES();
        saProcess.nLength = (uint)Marshal.SizeOf(saProcess);
        saThread.nLength = (uint)Marshal.SizeOf(saThread);

        STARTUPINFO si = new STARTUPINFO();
        si.cb = (uint)Marshal.SizeOf(si);

        //if this member is NULL, the new process inherits the desktop
        //and window station of its parent process. If this member is
        //an empty string, the process does not inherit the desktop and
        //window station of its parent process; instead, the system
        //determines if a new desktop and window station need to be created.
        //If the impersonated user already has a desktop, the system uses the
        //existing desktop.

        si.lpDesktop = @"WinSta0\Default"; //Default Vista/7 Desktop Session
        si.dwFlags = STARTF_USESHOWWINDOW | STARTF_FORCEONFEEDBACK;

        //Check the Startup Mode of the Process 
        if (WindowMode == 1)
            si.wShowWindow = SW_SHOW;
        else if (WindowMode == 2)
        { //Do Nothing
        }
        else if (WindowMode == 3)
            si.wShowWindow = 0; //Hide Window 
        else if (WindowMode == 4)
            si.wShowWindow = 3; //Maximize Window
        else if (WindowMode == 5)
            si.wShowWindow = 6; //Minimize Window
        else
            si.wShowWindow = SW_SHOW;


        //Set other si properties as required.
        result = CreateProcessAsUser(
        token,
        null,
        cmdLine,
        ref saProcess,
        ref saThread,
        false,
        CREATE_UNICODE_ENVIRONMENT,
        envBlock,
        null,
        ref si,
        out pi);

        if (result == false)
        {
            int error = Marshal.GetLastWin32Error();
            string message = String.Format("CreateProcessAsUser Error: {0}", error);
            Debug.WriteLine(message);

        }

        return result;
    }