App Object for Visual Basic 6.0 Users

Artikel
09/03/2015

This topic compares the Visual Basic 6.0 App object with its equivalent in Visual Basic 2008.

The App object in Visual Basic 6.0 is a global object used to set or retrieve information about the application. There is no direct equivalent for the App object in Visual Basic 2008. However, most of the properties, methods, and events can be mapped to equivalent members in the .NET Framework.

Conceptual Differences

Version Information Properties

The App object's Version Information properties are replaced by Assembly attributes in Visual Basic 2008. Version Information properties are set in the Project Properties dialog box. Assembly attributes are set in the Assembly Information dialog box, which is available by clicking the Application Information button on the Application tab of the Project Designer.

Note

Version Information properties are stored in the Project (.vbp) file, which you can edit using a text editor such as Notepad. Assembly attributes are stored in the AssemblyInfo.vb file and can be edited in the Code Editor.

File Description Property

The Visual Basic 6.0 App object has both FileDescription and Title properties; FileDescription determines the description text that appears in Windows Explorer.

In Visual Basic 2008, there is no FileDescription attribute. Instead, the Title attribute determines the descriptive text that appears in Windows Explorer.

HelpFile Property

The HelpFile property in Visual Basic 6.0 specifies a Help file at the application level.

In Visual Basic 2008, Help files are specified on a per-form basis using a HelpProvider component. For more information, see Help Support for Visual Basic 6.0 Users.

Version Properties

The Major, Minor, and Revision properties in Visual Basic 6.0 are used to return a three-part version number for an application.

In Visual Basic 2008, version information also includes a Build property, and the complete four-part version number can be retrieved using a single Version property. For more information, see Version Numbering for Visual Basic 6.0 Users.

Title Property

The Title property of the App object in Visual Basic 6.0 can be changed programmatically; doing so determines the name that appears in the Windows Task Manager.

In Visual Basic 2008, the Title attribute is read-only. The Text property of the application's main form determines the name that is shown in the Task Manager. You can set the Text property programmatically, but the text in the title bar of the form will change as well.

TaskVisible Property

In Visual Basic 6.0, the TaskVisible property of the App object determines whether an application appears in the Windows Task List (Windows 9x) or the Task Manager Applications tab (Windows 2000 or later). The property is commonly used to prevent a user from closing an application that was designed to run as a background task. In most cases, the TaskVisible property is used with applications that do not display user interfaces.

In Visual Basic 2008, there is no equivalent for the TaskVisible property; however, you can create a Windows Service or a Console Application that will not show up in the task list.

PrevInstance Property

The PrevInstance property in Visual Basic 6.0 determines if an instance of the application is already running. Typically you call PrevInstance on application startup and abort the application if it returns true.

There is no direct equivalent for PrevInstance in Visual Basic 2008. You control whether or not multiple instances of an application are allowed by setting the Multiple Instance property on the Application tab of the Project Designer. At run time, a NextInstanceStarted event is raised when a user tries to start another instance of the application. You can add code to this event handler to activate the first instance of the application.

Additional Differences

There are a number of App object properties in Visual Basic 6.0 that concern ActiveX components, OLE automation, and other technologies that are now obsolete and are not supported in Visual Basic 2008. They are noted in the App Object Property Equivalencies table later in this topic.

Code Changes for the App Object

The following code examples illustrate the differences in coding techniques between Visual Basic 6.0 and Visual Basic 2008 for some common uses of the App object.

Code changes for displaying an application's version number

The following example demonstrates retrieving an application's version number and displaying it in a label.

' Visual Basic 6.0
Label1.Caption = "Version: " & App.Major & "." & App.Minor & "." _
& App.Revision

' Visual Basic
Label1.Text = My.Application.Info.Version.ToString()

Code changes for determining an application's path

The following example demonstrates how to display an image file that is stored in the application's folder by retrieving the path to the executing application.

' Visual Basic 6.0
Picture1.Picture = LoadPicture(App.Path & "\Logo.jpg")

' Visual Basic
PictureBox1.Image = System.Drawing.Bitmap.FromFile( _
  My.Application.Info.DirectoryPath & "\Logo.jpg")

Code changes for preventing a second instance of an application from running

The following example demonstrates implementing a single-instance application.

' Visual Basic 6.0
Private Sub Form_Load()
    If App.PrevInstance = True Then
        MsgBox("The application is already running!")
    End If
End Sub

' Visual Basic' Assumes that the Make Single Instance Application checkbox in the ' Project Designer has been checked.PrivateSub MyApplication_StartupNextInstance(ByVal sender AsObject, _
ByVal e As Microsoft.VisualBasic.ApplicationServices. _
StartupNextInstanceEventArgs) HandlesMe.StartupNextInstance
    MsgBox("The application is already running!")
EndSub

App Object Property Equivalents

The following table lists all properties and methods of the Visual Basic 6.0 App object and their Visual Basic 2008 equivalents.

Visual Basic 6.0	Visual Basic 2008 Equivalent
Comments	My.Application.Info.Description Property
CompanyName	My.Application.Info.CompanyName Property
EXEName	My.Application.Info.AssemblyName Property
FileDescription	My.Application.Info.Title Property
HelpFile	New implementation. Use a HelpProvider component. For more information, see Help Support for Visual Basic 6.0 Users.
HInstance	GetHINSTANCE
LegalCopyright	My.Application.Info.Copyright Property
LegalTrademarks	My.Application.Info.Trademark Property
LogEvent method	WriteEntry Method (My.Application.Log and My.Log)
LogMode LogPath	New implementation. For more information, see Logging Information from the Application.
Major	My.Application.Info.Version Property Note: The format for version numbers is different in Visual Basic 2008. For more information, see Version Numbering for Visual Basic 6.0 Users.
Minor	My.Application.Info.Version Property Note: The format for version numbers is different in Visual Basic 2008. For more information, see Version Numbering for Visual Basic 6.0 Users.
NonModalAllowed	New implementation. This is a read-only property related to ActiveX .dll files. The common language runtime automatically manages this behavior.
OleRequestPendingMsgText OleRequestPendingMsgTitle OleRequestPendingTimeout OleServerBusyMsgText OleServerBusyMsgTitle OleServerBusyRaiseError OleServerBusyTimeout	No equivalent. These properties relate to OLE automation, which is not supported by Visual Basic 2008.
Path	My.Application.Info.DirectoryPath Property
PrevInstance	IsSingleInstance Note: The IsSingleInstance property is a Protected property. It can only be set at design time in the Project Designer by checking or clearing the Multiple Instance check box.
ProductName	My.Application.Info.ProductName Property
RetainedProject	New implementation. Visual Basic 2008 cannot retain a project in memory.
Revision	My.Application.Info.Version Property Note: The format for version numbers is different in Visual Basic 2008. For more information, see Version Numbering for Visual Basic 6.0 Users.
StartLogging method	New implementation. For more information, see Logging Information from the Application.
StartMode	No equivalent. This property concerns creating ActiveX components, which is not supported in Visual Basic 2008.
TaskVisible	New implementation. To create an application that does not appear in the Task Manager, create a Windows Service or Console Application project.
ThreadID	New implementation. This property returned the ID of the executing thread; the threading model is significantly different in Visual Basic 2008.
Title	My.Application.Info.Title Property
UnattendedApp	New implementation. For unattended applications in Visual Basic 2008, create a Console Application project.

Upgrade Notes

When an application is upgraded from Visual Basic 6.0, only the Major and Minor properties are upgraded; Visual Basic 2008 assigns new values to the Revision and Build properties.

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