Question

The answer probably involves a custom uninstall action, but it seems like such a major oversite and something that every application would want, so I thought I’d see if there is something easy I am missing.

I have a couple of projects create in Visual Studio 2008 using C#, Winform projects. One uses click-once install, and one use a setup project. They both allow you to leave the application running when you uninstall. On Windows 7 you do get a warning, but have the option to leave it running anyway… on XP not even a warning.

Call me crazy, but the thought of all of my program files being removed, and my app still left running, doesn’t sound like a good design at all. Memories of GPFs come to mind, or the way .NET uses delay loading for DLLs, also could be a problem when the DLL needs to be loaded, and is gone.

So is there an easy way to not allow uninstall if your app is still running?

I’m using C# but I’m using the VB.NET Single Instance class to make sure my app only runs once, so maybe something that takes advantage of that as opposed to creating a mutex to check for?

Also my app only allows “per user” installs, not “all users”, so I shouldn’t have to worry about my app running in another session (if it is, it is OK to stay running because it should be 100% its own copy).

Edit: Since I’m not finding anything else, I’ve tried the mutex idea and it isn’t working. Here is my code:

In the app I have this to create the named mutex and keep alive while app running:

        System.Threading.Mutex m = new System.Threading.Mutex(true, "SafeShare");

        SingleInstanceApplication.Run(TabForm, NewInstanceHandler);

        GC.KeepAlive(m);

In the uninstall action I have this to loop until they exit (since it doesn’t appear to be easy to provide a cancel option):

            while (true)
            {
                bool createdNew;
                System.Threading.Mutex m = new System.Threading.Mutex(true, "SafeShare", out createdNew);
                m.ReleaseMutex();
                if (createdNew)
                    break;
                MessageBox.Show(null,"Close XXX and click OK to continue uninstall.","Uninstall");
            }

createdNew is never set in the uninstall action, almost like it is running under a different session or something. I haven’t tried adding Global\ to the mutex name, but that would not work well for my app anyway because I do per-user installs, so one install should be able to keep running on another session even if one is uninstalled.

Answer 1

Short answer is there is no easy way to do this because it isn’t something Microsoft wants you to do.

My answer did end up using a mutex, once I got the code correct it seems to work fine.

In the app I do:

System.Threading.Mutex m = new System.Threading.Mutex(true, "MyMutexNameHere");
SingleInstanceApplication.Run(TabForm, NewInstanceHandler);
GC.KeepAlive(m); 

The SingleInstanceApplication.Run line is what runs your app, I’m using the VB.NET framework.

In the custom uninstall action I do:

while (true)
{
   bool createdNew;
   System.Threading.Mutex m = new System.Threading.Mutex(true, "MyMutexNameHere", out createdNew);
   m.Close();
   if (createdNew)
      break;
   MessageBox.Show(null,"Close XXX and click OK to continue uninstall.","Uninstall");
}    

At first I was using m.ReleaseMutex() instead of m.Close() which I found out was throwing an exception because I didn’t own the mutex. Close was what I should have been using, just to make sure my copy was closed before I checked again (otherwise createNew was never true, if it wasn’t true the first time).