Using ArcObjects to get Unique Values from a Table¶
| date: | 2007-02-25 16:35 |
|---|---|
| author: | geographika |
| category: | arcobjects |
| slug: | using-arcobjects-to-get-unique-values-from-a-table |
| status: | published |
A common requirement in many user dialogs is to display a list of unique values from a table, in order to delete or select records. While it is often easier to use Microsoft’s data objects, I try to use ArcObjects as the relevant libraries will always be installed on a user’s machine. The function will normally part of a larger project and I don’t like mixing the two methods to retrieve values from tables. I usually reuse a custom class for dealing with different types of geodatabases so that if a client changes from Access to SQL Server code changes will be minimal. Keeping up with changes to ESRI’s data access objects and Microsoft’s in the same project could get nasty..
There is a VBA / VB6 sample on how to get unique values at the EDN Site - but no .NET equivalent, hence my code sample below. There are no major changes except now a standard System.Collections enumerator is used rather than the ESRI IEnumVariantSimple.
Public Sub ListUniqueRecords()
Dim pMyTable As ITable
Dim pCurs As ICursor = Nothing
Dim intFieldIdx As Integer
Dim pDataStatistics As IDataStatistics
Dim pEnumVar As IEnumerator
Dim pWorkspaceFactory As IWorkspaceFactory
Dim pWorkspace As IWorkspace
Dim pFeatWorkSpace As IFeatureWorkspace
Dim strMyField As String = “VAL”
Try
pWorkspaceFactory = New AccessWorkspaceFactory
pWorkspace = pWorkspaceFactory.OpenFromFile(“C:\MyPath\MyGDB.mdb”, 0)
pFeatWorkSpace = CType(pWorkspace, IFeatureWorkspace)
pMyTable = pFeatWorkSpace.OpenTable(“MyTableName”)
intFieldIdx = pMyTable.FindField(strMyField)
pCurs = pMyTable.Search(Nothing, True)
pDataStatistics = New DataStatistics
pDataStatistics.Field = strMyField
pDataStatistics.Cursor = pCurs
pEnumVar = CType(pDataStatistics.UniqueValues, IEnumerator)
Do Until pEnumVar.MoveNext = False
Debug.Print(pEnumVar.Current.ToString)
Loop
Catch ex As Exception
Trace.WriteLine(ex.ToString)
Finally
‘clean up
pCurs = Nothing
pWorkspace = Nothing
End Try
End Sub
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