C# - Making a Process.Start wait until the process has start-up

Question

I need to make sure that a process is running before moving on with a method.

The statement is:

Process.Start(\"popup.exe\");

Can y

Answer 1

Are you sure the Start method returns before the child process starts? I was always under the impression that Start starts the child process synchronously.

If you want to wait until your child process finishes some sort of initialization then you need inter-process communication - see Interprocess communication for Windows in C# (.NET 2.0).

Answer 2

You can also check if the started process is responsive or not by trying something like this: while(process.responding)

Answer 3

I agree with Tom. In addition, to check the processes while performing Thread.Sleep, check the running processes. Something like:

bool found = 0;
while (!found)
{
    foreach (Process clsProcess in Process.GetProcesses())
        if (clsProcess.Name == Name)
            found = true;

    Thread.CurrentThread.Sleep(1000);
}

Answer 4

public static class WinApi
{

    [DllImport("user32.dll")]
    public static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

    public static class Windows
    {
        public const int NORMAL = 1;
        public const int HIDE = 0;
        public const int RESTORE = 9;
        public const int SHOW = 5;
        public const int MAXIMIXED = 3;
    }

}

App

String process_name = "notepad"
Process process;
process = Process.Start( process_name );

while (!WinApi.ShowWindow(process.MainWindowHandle, WinApi.Windows.NORMAL))
{
    Thread.Sleep(100);
    process.Refresh();
}

// Done!
// Continue your code here ...

Answer 5

Do you mean wait until it's done? Then use Process.WaitForExit:

var process = new Process {
    StartInfo = new ProcessStartInfo {
        FileName = "popup.exe"
    }
};
process.Start();
process.WaitForExit();

Alternatively, if it's an application with a UI that you are waiting to enter into a message loop, you can say:

process.Start();
process.WaitForInputIdle();

Lastly, if neither of these apply, just Thread.Sleep for some reasonable amount of time:

process.Start();
Thread.Sleep(1000); // sleep for one second

Answer 6

Here an implementation that uses a System.Threading.Timer. Maybe a bit much for its purpose.

    private static bool StartProcess(string filePath, string processName)
    {
        if (!File.Exists(filePath))
            throw new InvalidOperationException($"Unknown filepath: {(string.IsNullOrEmpty(filePath) ? "EMPTY PATH" : filePath)}");

        var isRunning = false;

        using (var resetEvent = new ManualResetEvent(false))
        {

            void Callback(object state)
            {
                if (!IsProcessActive(processName)) return;
                isRunning = true;
                // ReSharper disable once AccessToDisposedClosure
                resetEvent.Set();
            }

            using (new Timer(Callback, null, 0, TimeSpan.FromSeconds(0.5).Milliseconds))
            {
                Process.Start(filePath);
                WaitHandle.WaitAny(new WaitHandle[] { resetEvent }, TimeSpan.FromSeconds(9));
            }
        }

        return isRunning;
    }

    private static bool StopProcess(string processName)
    {
        if (!IsProcessActive(processName)) return true;

        var isRunning = true;

        using (var resetEvent = new ManualResetEvent(false))
        {

            void Callback(object state)
            {
                if (IsProcessActive(processName)) return;
                isRunning = false;
                // ReSharper disable once AccessToDisposedClosure
                resetEvent.Set();
            }

            using (new Timer(Callback, null, 0, TimeSpan.FromSeconds(0.5).Milliseconds))
            {
                foreach (var process in Process.GetProcessesByName(processName))
                    process.Kill();
                WaitHandle.WaitAny(new WaitHandle[] { resetEvent }, TimeSpan.FromSeconds(9));
            }
        }

        return isRunning;
    }

    private static bool IsProcessActive(string processName)
    {
        return Process.GetProcessesByName(processName).Any();
    }