I want to export a query to a Shapefile. If the query is empty I get an error and it will not export. How can I do nothing if the query is empty and export next query in the list?

Sample if I exporting Land but it is no Building on the land I get error

Export_with_query("2", "BUILDING", "1")

Export_with_query("2", "LAND", "1")

  Public Sub Export_with_query(ByVal ep_layer, ByVal ep_name, ByVal ep_query)

    Dim pDoc As IMxDocument
    Dim pMap As IMap
    Dim pFLayer As IFeatureLayer
    Dim pFc As IFeatureClass
    Dim pINFeatureClassName As IFeatureClassName
    Dim pDataset As IDataset
    Dim pInDsName As IDatasetName
    Dim pFSel As IFeatureSelection
    Dim pSelSet As ISelectionSet
    Dim pFeatureClassName As IFeatureClassName
    Dim pOutDatasetName As IDatasetName
    Dim pWorkspaceName As IWorkspaceName
    '   Dim pExportOp As IExportOperation
    Dim pExportOp As ESRI.ArcGIS.GeoDatabaseUI.IExportOperation


        pDoc = My.ArcMap.Document
        pMap = pDoc.FocusMap
        pFLayer = pMap.Layer(ep_layer)
        pFc = pFLayer.FeatureClass

        'Get the FcName from the featureclass
        pDataset = pFc
        pINFeatureClassName = pDataset.FullName
        pInDsName = pINFeatureClassName

        'Get the selection set
        pFSel = pFLayer
        pSelSet = pFSel.SelectionSet

        Dim pQFilter As IQueryFilter
        pQFilter = New QueryFilter
        pQFilter.WhereClause = "TYPE =  '" & ep_query & "'"
        If pFc.FeatureCount(pQFilter) = 0 Then
            Exit Sub

        'Define the output feature class name
        pFeatureClassName = New FeatureClassName
        pOutDatasetName = pFeatureClassName
        pOutDatasetName.Name = ep_name
        pWorkspaceName = New WorkspaceName
        If Chk_default_path.Checked = True Then
            pWorkspaceName.PathName = "c:\map"
            pWorkspaceName.PathName = Txt_path.Text
        End If
        pWorkspaceName.WorkspaceFactoryProgID = _
        pOutDatasetName.WorkspaceName = pWorkspaceName
        'pFeatureClassName.FeatureType = esriFTSimple
        pFeatureClassName.FeatureType = ESRI.ArcGIS.Geodatabase.esriFeatureType.esriFTSimple
        '  pFeatureClassName.ShapeType = esriGeometryAny
        pFeatureClassName.ShapeType = ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryAny
        pFeatureClassName.ShapeFieldName = "Shape"

        ' pExportOp = New ExportOperation
        pExportOp = New ESRI.ArcGIS.GeoDatabaseUI.ExportOperation
        ' pExportOp.ExportFeatureClass(pInDsName, Nothing, pSelSet, Nothing, pOutDatasetName, 0)

        pExportOp.ExportFeatureClass(pInDsName, pQFilter, pSelSet, Nothing, pOutDatasetName, 0)
        'pExportOp.ExportFeatureClass(pInFClassName, pQFilter, pSelSet, pGeomDef, pOutDatasetName, 0)
        '   End If

    Catch ex As Exception
        MessageBox.Show("Error exporting map: " & vbCrLf & ex.ToString)
    End Try
End Sub

You get the selection set on the feature layer but then you do a feature count on the feature class, an object that does not support selections. So your current logic makes no sense.

Now do you want to export an EXISTING selection or do you want to SELECT then export?

If you want to export an existing selection then delete the Featurecount code as that is not doing anything for you.

You would need to write:

'Get the selection set
pFSel = pFLayer
pSelSet = pFSel.SelectionSet
If pSelSet.Count = 0 then
    Exit Sub
End if

If you want to SELECT and then export I would use code:

Dim pQFilter As IQueryFilter
pQFilter = New QueryFilter
pQFilter.WhereClause = "TYPE =  '" & ep_query & "'"
pSelSet = pFSel.SelectionSet
If pSelSet.Count = 0 then
    Exit Sub
End if
| improve this answer | |
  • Like it, you've got both ways here: an existing selection and creating a new selection based on a query. Just be aware that the featureselection is iterated on IEnumFeature and the selection set is iterated using an IFeatureCursor - both iterate IFeature objects but their next one approaches are different... you will need to keep track of which one you're using (a boolean works here) and either IFeatureCursor.NextFeature() or IEnumFeature.Next() as appropriate. – Michael Stimson Nov 5 '14 at 21:39
  • Thanks for the help I am using select By Graphics to mark the area I want to export so I am finish to Select few layer to export I don't get the error anymore but I export to much outside the area I mark with Select By Graphics – Sigster Nov 6 '14 at 8:34
  • The first one works :) Hornbydd, artwork21 Thanks for your help with this ! Regards Sigster – Sigster Nov 6 '14 at 8:43

You will have to use an if statement to check the feature count using IFeatureClass.FeatureCount Method, before exporting.

| improve this answer | |
  • 1
    I try to use this it just ignore it :) If pFc.FeatureCount(pQFilter) = 0 Then Exit Sub Else – Sigster Nov 5 '14 at 18:11
  • Can you update your code snippet with the logic included? – artwork21 Nov 5 '14 at 18:45

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