How do I restart my C# WinForm Application?

I had the same exact problem and I too had a requirement to prevent duplicate instances - I propose an alternative solution to the one HiredMind is proposing (which will work fine).

What I am doing is starting the new process with the processId of the old process (the one that triggers the restart) as a cmd line argument:

// Shut down the current app instance.
Application.Exit();

// Restart the app passing "/restart [processId]" as cmd line args
Process.Start(Application.ExecutablePath, "/restart" + Process.GetCurrentProcess().Id);

Then when the new app starts I first parse the cm line args and check if the restart flag is there with a processId, then wait for that process to Exit:

if (_isRestart)
{
   try
   {
      // get old process and wait UP TO 5 secs then give up!
      Process oldProcess = Process.GetProcessById(_restartProcessId);
      oldProcess.WaitForExit(5000);
   }
   catch (Exception ex)
   { 
      // the process did not exist - probably already closed!
      //TODO: --> LOG
   }
}

I am obviously not showing all the safety checks that I have in place etc.

Even if not ideal - I find this a valid alternative so that you don't have to have in place a separate app just to handle restart.

Start/Exit Method

// Get the parameters/arguments passed to program if any
string arguments = string.Empty;
string[] args = Environment.GetCommandLineArgs();
for (int i = 1; i < args.Length; i++) // args[0] is always exe path/filename
    arguments += args[i] + " ";

// Restart current application, with same arguments/parameters
Application.Exit();
System.Diagnostics.Process.Start(Application.ExecutablePath, arguments);

This seems to work better than Application.Restart();

Not sure how this handles if your program protects against multiple instance. My guess is you would be better off launching a second .exe which pauses and then starts your main application for you.

You are forgetting the command-line options/parameters that were passed in to your currently running instance. If you don't pass those in, you are not doing a real restart. Set the Process.StartInfo with a clone of your process' parameters, then do a start.

For example, if your process was started as myexe -f -nosplash myfile.txt, your method would only execute myexe without all those flags and parameters.

Here's my 2 cents:

The sequence Start New Instance->Close Current Instance should work even for the applications that don't allow running multiple copies simultaneously as in this case the new instance may be passed a command-line argument which will indicate that there is a restart in progress so checking for other instances running will not be necessary. Waiting for the first instance to actually finish my be implemented too if it's absolutely imperative that no two intstances are running in parallel.

You could enclose your code inside a function and when restart is needed you can just call the function.

Take for instance an application that:

1. While application is not registered; (upon start) the application should prompt the user to register the application and create a login account.

2. Once registration is submitted and login credentials are created; the application should restart, check for registration and prompt the user to login with the inserted credentials (so the user can access to all the application features).

Problem: By building and launching the application from Visual Studio; any of the 4 alternatives bellow will fail to accomplish the tasks required.

/*
 * Note(s):
 * Take into consideration that the lines bellow don't represent a code block.
 * They are just a representation of possibilities,
 * that can be used to restart the application.
 */

Application.Restart();
Application.Exit();
Environment.Exit(int errorCode);
Process.GetCurrentProcess().Kill();

What happens is: After creating the Registration, Login and calling Application.Restart(); the application will (strangely) reopen the Registration Form and skip data in a Database (even though the resource is set to "Copy if Newer").

Solution: Batch Building the application was (for me) a proof that any of the lines above were actually working as expected. Just not when building and running the application with Visual Studio.

In first place I'd try batch building the application; run it outside Visual Studio and check if Application.Restart() actually works as expected.

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