ArcGIS Engine Developer Guide

INTERFACES AND MEMBERS
error message “Run-time error ‘13’ ; Type mismatch”.
Dim pGxApp As IGxApplication
Set pGxApp = Application
Dim pGxV As IGxView
Set pGxV = pGxApp.TreeView
'Optional interface for GxViews
Dim pGxVP As IGxViewPrint
'Attempting to QI to this will result in a runtime error
Set pGxVP = pGxV
Interfaces implemented in select instances
esriGeoDatabase.-
IRasterDataset
esriGeoDatabase.-
IRasterDataset2
esriGeoDatabase.-
IRasterDatasetEdit
IRasterBand-
Collection
IRasterPyramid
ISaveAs
(Instance-File)
ITemporaryDataset
(Instance-File)
IWorldFileExport
(Instance-DB)
IRasterPyramid2
RasterDataset
The RasterDataset class and the interfaces it
implements when instantiated by file-based and
ArcSDE software-based data
Some classes have been designed to have varying implementations instead of
having multiple classes that inherit from a single base or abstract class. In these
cases, certain interfaces are implemented in select instances. For example, the
RasterDataset class can be instantiated by different Workspace classes depending on
the type of data being accessed. When file-based data is used to instantiate a
RasterDataset class, the ITemporaryDataset interface is implemented; however, if
ArcSDE software-based data is used to instantiate the RasterDataset class, the
IRasterPyramid2 interface isn’t implemented.
Interfaces that are implemented in select instances are designated with the prefix
(Instance). Attempts to access a selected instance interface that hasn’t been
implemented will produce a “Run-time error ‘13’ ; Type mismatch”.
Dim pWsFact As IWorkspaceFactory
Dim pWs As IRasterWorkspace
Dim pRasterDataset As IRasterDataset
'Open the workspace
Set pWsFact = New RasterWorkspaceFactory
Set pWs = pWsFact.OpenFromFile("D:\data\canada", 0)
'Open the raster dataset
Set pRasterDataset = pWs.OpenRasterDataset("Dem")
'Test if interface is implemented before QI
Dim pTempDS As ITemporaryDataset
If TypeOf pRasterDataset Is ITemporaryDataset Then
Set pTempDS = pRasterDataset
End If
OUTBOUND INTERFACES
Outbound interfaces, also known as event interfaces, provide notification when a
certain event occurs. Interaction with the members of an outbound interface
requires that another object exists to catch the event occurrences; this is commonly
referred to as an event sink. Event sinks have code that responds when
certain events occur, an editing operation, for example. In Visual Basic, the
creation of classes that will act as sinks to an outbound interface requires that the
outbound interface declaration include the name of the class that implements the
interface.
Private WithEvents EditEvents as Editor
Although the object variable has been declared with the class that will be raising
the events, it points to nothing. The object variable must be initialized using the
Appendix A • Reading the object model diagrams • 447