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Check if application already running in VB .NET

Posted on 2004-09-28
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Last Modified: 2013-12-26
The App.PrevInstance function is deprecated and no longer usable in .NET.  There is no equivalent, but the same result can be obtained via:

Public Function PrevInstance() As Boolean
  If Diagnostics.Process.GetProcessesByName _
     (Diagnostics.Process.GetCurrentProcess.ProcessName) _
               .Length > 1 Then
     Return True
  Else
     Return False
  End If
End Function

My problem is that whenever I make a call to the Diagnostics.Process.xxx objects, my application stalls and needs to be manually end tasked.  For trouble shooting purposes I have tried:
msgbox(Diagnostics.Process.GetCurrentProcess.ProcessName)
This also freezes the application.  Even a completely empty application with only one form and with this msgbox line in the form load function freezes.  Any ideas?

On another note, my application is one that runs solely in the system tray as a system tray icon, with no visible windows.  The way I have accomplished this is by setting the form that loads with the project to start minimized and then doing me.hide() on form load.  Is this a good/the right way to do this?

Thanks.
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Question by:JeffN825
1 Comment
 
LVL 86

Accepted Solution

by:
Mike Tomlinson earned 1500 total points
ID: 12176534
This worked correctly for me:

Public Class Form1
    Inherits System.Windows.Forms.Form

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If PrevInstance() Then
            MsgBox("another instance is running")
        End If
    End Sub

    Private Function PrevInstance() As Boolean
        If UBound(Diagnostics.Process.GetProcessesByName(Diagnostics.Process.GetCurrentProcess.ProcessName)) > 0 Then
            Return True
        Else
            Return False
        End If
    End Function

End Class
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