Prevent opening multiple instances of VB application

Question

My VB6 application is backed by a MS Access database. Allowing user to open multiple instances of the application would create conflicts & alter connected database.

Ideal solution would be to focus existing instance if user tries to open new one.

How can I attain this?

The term you need is "single instance application". – ChrisF Aug 12 '10 at 14:17 — ChrisF, Aug 12 '10 at 14:17

score 7 · Accepted Answer · edited Aug 12 '10 at 18:34

7

Use App.PrevInstance:

'this code would be in a bas module for start up.'
Private Sub main()
    'Check for previous instance and exit if found.'

    Dim rc As Long

    If App.PrevInstance Then
        rc = MsgBox("Application is already running", vbCritical, App.Title)
        Exit Sub
    Else
        frmMain.Show
    End If

End Sub

edited Aug 12 '10 at 18:34

Mike Spross

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answered Aug 12 '10 at 14:37

MusiGenesis

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Thanks, that worked perfectly, now is there anyway to set focus to current instance instead of showing error message..? – Kushal Aug 12 '10 at 15:21
Yeah, use the `AppActivate` method - pass in whatever's in the title bar of your application. – MusiGenesis Aug 12 '10 at 15:32

Prevent opening multiple instances of VB application

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