Check if app is already running

[Michael Passalacqua]

In VB.NET, how do you check to see if an instance of your application is
already running?

Michael Passalacqua
Portland Community College
CIS Faculty

*** Sent via Developersdex http://www.developersdex.com ***
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[meh]

If you make a public function similar to this

Public Shared Function PrevInstance() As Process

Dim c As Process = Process.GetCurrentProcess()

Dim p As Process

For Each p In Process.GetProcessesByName(c.ProcessName)

If p.Id <> c.Id Then

If p.MainModule.FileName = c.MainModule.FileName Then

Return p

End If

End If

Next p

Return Nothing

End Function

And then call it from say the Form load event or a sub main

If Not PrevInstance() Is Nothing Then

MsgBox("Myapp is already running !", MsgBoxStyle.Information, "Myapp")

End

' Else

' Exit.

End If

Hope this helps...

meh

"Michael Passalacqua" <mp******@pcc.edu> wrote in message news:e1*************@TK2MSFTNGP10.phx.gbl...

In VB.NET, how do you check to see if an instance of your application is
already running?

Michael Passalacqua
Portland Community College
CIS Faculty

*** Sent via Developersdex http://www.developersdex.com ***
Don't just participate in USENET...get rewarded for it!

[Armin Zingler]

"Michael Passalacqua" <mp******@pcc.edu> schrieb

In VB.NET, how do you check to see if an instance of your application
is already running?

It's been asked and answered two hours ago. Subject: Is app already running?
--
Armin

[Herfried K. Wagner [MVP]]

* Michael Passalacqua <mp******@pcc.edu> scripsit:

In VB.NET, how do you check to see if an instance of your application is
already running?

<http://www.google.com/groups?selm=blgrft%24c51nq%244%40ID-208219.news.uni-berlin.de>

--
Herfried K. Wagner
MVP · VB Classic, VB.NET
<http://www.mvps.org/dotnet>

[rgsiii]

Unfortunately, even checking file paths is not fullproof.

If you really want to prevent multiple instances, regardless of if the myApp.exe is in a different folder, or even if they rename the file, then you have to take a different approach.

One of the easier solutions is to set up a OS level named Mutex and check that when the app starts.

The following c# code demonstrates (which can be easily translated into vb.net if desired):

Mutex myMutex = null;
 
//ensure that the app is not already running!
//this method will prevent duplicates, even if the user has
//changed the exe name.  This method is more reliable than just
//checking for process name in the process list!
try
{
    Console.WriteLine("Checking to see if app is already running...");
    reeMutex = Mutex.OpenExisting( "myMutexName" );
    //if we were able to open the mutex
    //that means that it already existed
    //which means that the app is already running
    //which means we need to abaondon ship
 
    Console.WriteLine( Process.GetCurrentProcess().MainModule.FileName + " is already running! Only a single MyApp can run at a time. This instance will shut down." );
    return ;
 
}
catch( WaitHandleCannotBeOpenedException )
{
    //This is the FIRST instantiation, 
    //which means that this is the first run of the app
    //which means we can keep on running
    //so go ahead and create the mutex
    Console.WriteLine( "Mutex does not exist, creating..." );
    bool mutexWasCreated = false;
    reeMutex = new System.Threading.Mutex( true, mutexName, out mutexWasCreated );
 
}
catch( UnauthorizedAccessException )
{
    //if there was a security access error
    //that means that it already existed (even though we could't open it)
    //which means that the appis already running
    //which means we need to abaondon ship
 
    Console.WriteLine( Process.GetCurrentProcess().MainModule.FileName + " is already running! Only a single MyApp can run at a time. This instance will shut down." );
    return;
 
}
 

Enjoy!
Robert