WindowsFormsApplicationBase::StartupNextInstance Event

.NET Framework (current version)
 

Occurs when attempting to start a single-instance application and the application is already active.

Namespace:   Microsoft.VisualBasic.ApplicationServices
Assembly:  Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)

C#
C++
F#
VB
Copy 
public:
event StartupNextInstanceEventHandler^ StartupNextInstance {
	void add(StartupNextInstanceEventHandler^ value);
	void remove(StartupNextInstanceEventHandler^ value);
}

A single-instance application raises the StartupNextInstance event when you attempt to restart the application when it is already active. When a single-instance application starts for the first time, it raises the Startup event. For more information, see Startup.

This event is part of the Visual Basic Application model. For more information, see Overview of the Visual Basic Application Model.

This event is raised on the application's main thread with the other user-interface events. This allows the event handler to access directly the application's user interface. However, if the application is busy handling another user-interface event when this event is raised, this event cannot be processed until the other event handler finishes or calls the DoEvents method.

System_CAPS_noteNote

The StartupNextInstance event is raised only in single-instance applications. To enable single-instance behavior for your application, you must check the Make single instance application check box in the Project Designer.

To make an application single instance

  1. With a project selected in Solution Explorer, click Properties on the Project menu.

  2. Click the Application tab.

  3. Select the Make single instance application check box.

You must use the CommandLine property of the e parameter to access the arguments for subsequent attempts to start a single-instance application. The CommandLineArgs property provides the arguments used to start the first instance of a single-instance application.

The code for the StartupNextInstance event handler is stored in the ApplicationEvents.vb file, which is hidden by default.

To access the Code Editor window for application events

  1. With a project selected in Solution Explorer, click Properties on the Project menu.

  2. Click the Application tab.

  3. Click the View Application Events button to open the Code Editor.

    For more information, see Application Page, Project Designer (Visual Basic).

The following table lists examples of tasks involving the My.Application.StartupNextInstance event.

To

See

Check the command-line arguments of the first application instance

CommandLineArgs

Project type

Available

Windows Forms Application

Yes

Class Library

No

Console Application

No

Windows Forms Control Library

No

Web Control Library

No

Windows Service

No

Web Site

No

This example uses the e parameter of the StartupNextInstance event handler to examine the application's command-line arguments. If an argument is found that starts with /input=, the rest of that argument is displayed.

VB
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Private Sub MyApplication_StartupNextInstance( 
    ByVal sender As Object, 
    ByVal e As Microsoft.VisualBasic.ApplicationServices.StartupNextInstanceEventArgs 
) Handles Me.StartupNextInstance
    Dim inputArgument As String = "/input="
    Dim inputName As String = ""

    For Each s As String In e.CommandLine
        If s.ToLower.StartsWith(inputArgument) Then
            inputName = s.Remove(0, inputArgument.Length)
        End If
    Next

    If inputName = "" Then
        MsgBox("No input name")
    Else
        MsgBox("Input name: " & inputName)
    End If
End Sub

You must enter the code in the Code Editor window for application events. To access this window, follow the instructions from this topic's Remarks section. For more information, see Application Page, Project Designer (Visual Basic).

.NET Framework
Available since 2.0
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