PrevInstance

Returns True if another instance of this executable was already running when the current instance started, or False if this is the only running instance. Read-only.

Syntax: object.PrevInstance

object

required An object expression that evaluates to an _App object. In practice this is the global App object.

Use PrevInstance to enforce a single-instance application. Check the value during startup — typically in Sub Main or the first form’s Load event — and exit if it returns True.

The detection is based on the executable’s file name and path, consistent with the Win32 FindWindow or mutex-based approaches used in classic VB6 projects.

Example

This example prevents a second instance of the application from running.

Sub Main()
    If App.PrevInstance Then
        MsgBox "Another instance of " & App.EXEName & " is already running.", vbExclamation
        End
    End If
    ' ... rest of startup
End Sub

See Also

• EXEName property
• IsInIDE property