ArcGIS Engine Developer Guide

THE V ISUAL BASIC 6 DEVELOPMENT ENVIRONMENT
Visual Basic automatically generates the
necessary GUIDs for the classes, interfaces, and
libraries. Setting binary compatibility forces VB to
reuse the GUIDs from a previous compilation of
the DLL. This is essential, since ArcMap stores
the GUIDs of commands in the document for
subsequent loading.
7. Compile the DLL.
8. Set the component’s Version Compatibility to binary. As your code evolves, it’s
good practice to set the components to Binary Compatibility so, if you make
changes to a component, you’ll be warned that you’re breaking compatibility.
For additional information, see the ‘Binary compatibility mode’ help topic in
the Visual Basic online help.
9. Save the project.
10. Make the component available to the application. You can add a component
to a document or template by clicking the Add from file button in the Customize
dialog box’s Commands tab. In addition, you can register a component
in the Component Category Manager.
IMPLEMENTING INTERFACES
You implement interfaces differently in Visual Basic, depending on whether they
are inbound or outbound interfaces. An outbound interface is seen by Visual
Basic as an event source and is supported through the WithEvents keyword. To
handle the outbound interface, IActiveViewEvents, in Visual Basic (the default
outbound interface of the Map class), use the WithEvents keyword and provide
appropriate functions to handle the events.
Private WithEvents ViewEvents As Map
Private Sub ViewEvents_SelectionChanged()
' User changed feature selection update my feature list form
UpdateMyFeatureForm
End Sub
Inbound interfaces are supported with the Implements keyword. However, unlike
the outbound interface, all the methods defined on the interface must be stubbed
out. This ensures that the vTable is correctly formed when the object is instantiated.
Not all the methods have to be fully coded, but the stub functions must be
there. If the implementation is blank, an appropriate return code should be given
to any client to inform them that the method is not implemented (see the section
‘Working with HRESULTs’ in this chapter). To implement the IExtension interface,
code similar to that below is required. Note that all the methods are implemented.
Private m_pApp As IApplication
Implements IExtension
Private Property Get IExtension_Name() As String
IExtension_Name = "Sample Extension"
End Property
Private Sub IExtension_Startup(ByRef initializationData As Variant)
Set m_pApp = initializationData
End Sub
Private Sub IExtension_Shutdown()
Set m_pApp = Nothing
End Sub
Chapter 4 • Developer environments • 93