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Visual Basic Reference

PrevInstance Property

See Also    Example    Applies To

Returns a value indicating whether a previous instance of an application is already running.



The object placeholder represents an object expression that evaluates to an object in the Applies To list.


You can use this property in a Load event procedure to specify whether a user is already running an instance of an application. Depending on the application, you might want only one instance running in the Microsoft Windows operating environment at a time.

Note   Since a computer running Windows NT can support multiple desktops, if you use a component designed to work with distributed COM, it can result in the following scenario:

  • A client program in a user desktop requests one of the objects the component provides. Because the component is physically located on the same machine, the component is started in the user desktop.

  • Subsequently, a client program on another computer uses distributed COM to request one of the objects the component provides. A second instance of the component is started, in a system desktop.

There are now two instances of the component running on the same NT computer, in different desktops.

This scenario is not a problem unless the author of the component has placed a test for App.PrevInstance in the startup code for the component to prevent multiple copies of the component from running on the same computer. In this case, the remote component creation will fail.