“make single instance application” what does this do?

Question

in vb 2008 express this option is available under application properties. does anyone know what is its function? does it make it so that it\'s impossible to open two instanc

Answer 1

Why not just use a Mutex? This is what MS suggests and I have used it for many-a-years with no issues.

Public Class Form1
Private objMutex As System.Threading.Mutex
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    'Check to prevent running twice
    objMutex = New System.Threading.Mutex(False, "MyApplicationName")
    If objMutex.WaitOne(0, False) = False Then
        objMutex.Close()
        objMutex = Nothing
        MessageBox.Show("Another instance is already running!")
        End
    End If
    'If you get to this point it's frist instance

End Sub
End Class

When the form, in this case, closes, the mutex is released and you can open another. This works even if you app crashes.