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.NET Forum / Languages / C# / December 2007how to check if app is already running?
Hi all I'd like to avoid starting the same c# application twice on the same computer. How do I check if it is already running? Thank you private void Test_Launcb() { Process [] localByName = Process.GetProcessesByName("ProgramName"); // Where ProgramName is the name of your Application if (localByName.Length > 1) // This copy makes 1 { Application.Exit(); } } Hope this helps Dan > Hi all > [quoted text clipped - 3 lines] > > Thank you Hello Dan, Take into account that this doesn't work in Terminal Services. In that case u need to use Global Mutex DT> private void Test_Launcb() DT> DT> { DT> DT> Process [] localByName = Process.GetProcessesByName("ProgramName"); DT> // Where ProgramName is the name of your Application DT> DT> if (localByName.Length > 1) // This copy makes 1 DT> DT> { DT> DT> Application.Exit(); DT> DT> } DT> DT> } DT> DT> Hope this helps DT> Dan DT> "Alex K." <AlexK@discussions.microsoft.com> wrote in message DT> news:1493C077-9AA3-4568-8C56-433B69F34F38@microsoft.com... DT> >> Hi all >> >> I'd like to avoid starting the same c# application twice on the same >> computer. >> How do I check if it is already running? >> Thank you --- WBR, Michael Nemtsev :: blog: http://spaces.live.com/laflour "At times one remains faithful to a cause only because its opponents do not cease to be insipid." (c) Friedrich Nietzsch It's also the worst way to do this. Scanning through the process list is VERY costly. It's easier to just set up a mutex that your app claims when your app starts, and block out subsequent runs of it if you can't acquire the mutex. See my other response for a more detailed way of doing this.  Signature- Nicholas Paldino [.NET/C# MVP] - mvp@spam.guard.caspershouse.com > Hello Dan, > [quoted text clipped - 29 lines] > "At times one remains faithful to a cause only because its opponents do > not cease to be insipid." (c) Friedrich Nietzsche | Hello Dan, | | Take into account that this doesn't work in Terminal Services. In that case | u need to use Global Mutex And TS means anything from XP and up. Willy. Alex, Here is a response to a different post which answers your question: http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/msg/0712 8f9ddd957ada Hope this helps. Signature- Nicholas Paldino [.NET/C# MVP] - mvp@spam.guard.caspershouse.com > Hi all > [quoted text clipped - 3 lines] > > Thank you Thanks Dan, it works! > Hi all > > I'd like to avoid starting the same c# application twice on the same computer. > How do I check if it is already running? > > Thank you > Thanks Dan, it works! Don't do it - go with the mutex approach, which is much more efficient... Can you supply the sample code for the mutex approach? BTW, this method works fine for TS and XP. I have 15 machines in my building alone as proof. Dan >> Thanks Dan, it works! > > Don't do it - go with the mutex approach, which is much more efficient... The number of machines running this isn't proof enough. If you have a minimal number of processes on each machine, it doesn't matter how many machines are running the app. In the end, the process approach can take up to O(n) time, where n is the number of processes on the machine. The mutex approach is always an O(1) operation. Always guaranteed to be more efficient. The Mutex approach is easy: public static void Main() { // Created? bool created = false; // Create the mutex. using (Mutex mutex = new Mutex(true, "MyMutex", out created)) { // If this is not created, get out. if (!created) { // Get out. return; } // Run your app code here. } } If you want your running app to handle command line parameters that are passed to new instances that are run, then you should look at the WindowsFormsApplicationBase class in the Microsoft.VisualBasic namespace, as it handles this for you. Signature- Nicholas Paldino [.NET/C# MVP] - mvp@spam.guard.caspershouse.com > Can you supply the sample code for the mutex approach? > [quoted text clipped - 6 lines] >> >> Don't do it - go with the mutex approach, which is much more efficient... Thanks for the sample. When I was referring to proof, I was talking about the program running on TS or XP. Someone on the thread said "Take into account that this doesn't work in Terminal Services." This is not true. I will most likely change my code to the Mutex method, but the other method does work. I agree the Mutex is more efficient, but if your talking about checking the running processes, ONLY when attempting to run the program, its unlikely this code will fire very often. My example was when a different user was logging into Windows. I wanted to suppress running the program again if another user already started it. This was especially important on a terminal services environment. Thanks Again Dan > The number of machines running this isn't proof enough. If you have a > minimal number of processes on each machine, it doesn't matter how many [quoted text clipped - 41 lines] >>> Don't do it - go with the mutex approach, which is much more >>> efficient... Hi, Windows XP Pro SP2, Workgroup The mutex approach doesn't always work for me. It works in the following scenarios: 1. User A attempts to launch a second instance of the process. User A launched the first instance (ie same user, same workstation) 2. User A attempts to launch a second instance of the process. User B launched the first instance. Both instances are running in the same workstation (e.g. RunAs was used to change the owner of one of the processes). It doesn't seem to work when user A attempts to launch a second instance of the process where user B launched the first instance in a different workstation (e.g. launch the process, switch to a different user (and therefore a different workstation) and launch a second instance of the process). I always thought that named mutexes provided exclusivity over the entire machine... I've already tried using the Mutex constructor that takes a Security object, granting full permission to everyone, but it made no difference. When I examine the mutex names using SysInternals' Process Explorer, the name that I gave the mutex is qualified and the qualifications are different on the two processes. Should a mutex work in this scenario? Dave Razzetti > The number of machines running this isn't proof enough. If you have a > minimal number of processes on each machine, it doesn't matter how many [quoted text clipped - 40 lines] > >> > >> Don't do it - go with the mutex approach, which is much more efficient... > Hi, > [quoted text clipped - 20 lines] > I always thought that named mutexes provided exclusivity over the entire > machine... Only if the mutex is of a global type like.... "Global\MyMutex" Willy. Thanks Willy, I'd just found an MSDN article that said exactly that! Isn't it funny how a minute or two after you post a question on here, you stumble across the solution somewhere else? Its happened a couple of times now... Dave Razzetti > > Hi, > > [quoted text clipped - 25 lines] > > Willy. > Can you supply the sample code for the mutex approach? 1) Launch your Internet browser (IE, FireFox, Netscape, Opera Mozilla etc) 2) Navigate to http://www.google.com 3) Enter the text below in the box: "C#" "global mutex" prevent twice 4) Hit the button > BTW, this method works fine for TS and XP. I have 15 machines in my > building alone as proof. Of course it does - it's just not particularly efficient... Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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