Use an IFeatureCursor with IQueryDef

Summary

To use an IQueryDef with an IFeatureCursor, you assign a name to the QueryDef using IFeatureContainer and use this name like a feature class name.

Procedure

The following code connects to a geodatabase, sets up an IQueryDef, and does a table join between the counties feature class and the farms table. Note only three fields are included in the subfields: the shape, and one field from each table. These columns are the only fields that can be accessed through the IQueryDef object. A IFeatureClassContainer is used to assign the name MyJoin to the IQueryDef. This name is used to open an IFeatureCursor.

Private Sub Connect2GDB()Sub Connect2GDB()
'-- Connect to Ggodatabase (SDE)
  Dim pPropset As IPropertySet
  Set pPropset = New PropertySet
  With pPropset
    .SetProperty "Server", "testserver"
    .SetProperty "Instance", "5250"
    .SetProperty "Database", ""
    .SetProperty "user", "test"
    .SetProperty "password", "test"
    .SetProperty "version", "SDE.DEFAULT"
  End With
        
  Dim pFact As IWorkspaceFactory
  Set pFact = New SdeWorkspaceFactory
    
  '-- Open the feature dataset
  Dim pWorkspace As IWorkspace
  Set pWorkspace = pFact.Open(pPropset, Me.hWnd)
    
  '-- Create feature workspace
  Dim pFeatureWorkspace As IFeatureWorkspace
  Set pFeatureWorkspace = pWorkspace
    
  '-- Create query definition
  Dim pQueryDef As IQueryDef
  Set pQueryDef = pFeatureWorkspace.CreateQueryDef
    
  '-- Provide list of tables to join
  pQueryDef.Tables = "counties,farms"
    
  '-- Retrieve the fields from all  tables
  pQueryDef.SubFields = "shape,counties.name,farms.NO_FARMS87"
    
  '-- Set up join
  pQueryDef.WhereClause = "counties.fips = farms.fips"
    
  '-- Create FeatureDataset. Note the use of .OpenFeatureQuery. The
  '-- MyJoin name was the result of the query def and is used in
  '-- place of a feature class name.
  Dim pFeatureDataset As IFeatureDataset
  Set pFeatureDataset = pFeatureWorkspace.OpenFeatureQuery("MyJoin", pQueryDef)
    
  '-- Open Layer to test against
  Dim pFeatureClassContainer As IFeatureClassContainer
  Set pFeatureClassContainer = pFeatureDataset
     
  Dim pFeatureClass As IFeatureClass
  Set pFeatureClass = pFeatureClassContainer.ClassByName("MyJoin")
    
  Dim pFeatureCursor As IFeatureCursor
  Set pFeatureCursor = pFeatureClass.Search(Nothing, True)

End Sub