I am following the sample code from ESRI for checking topology errors using vb.net. But in my workspace an error happened. My code is listed below:

   ' Step 1 - access a topology
    Dim topoUiD As UID = New UIDClass
    topoUiD.Value = "esriEditorExt.TopologyExtension"
    Dim m_application As IApplication = My.ArcMap.Application
    Dim topologyExt As ITopologyExtension = CType(m_application.FindExtensionByCLSID(topoUiD), ITopologyExtension)  'original code from esri
    Dim topology As ITopology
    topology = CType(topologyExt.CurrentTopology, ITopology)

    ' Step 2 - Finding topology errors
    Dim geoDS As IGeoDataset = CType(topology, IGeoDataset)
    Dim errorContainer As IErrorFeatureContainer = CType(topology, IErrorFeatureContainer)
    Dim eErrorFeat As IEnumTopologyErrorFeature
    eErrorFeat = errorContainer.ErrorFeaturesByRuleType(geoDS.SpatialReference, esriTopologyRuleType.esriTRTLineCoveredByLineClass, Nothing, True, False)
    Dim topoError As ITopologyErrorFeature

    topoError = eErrorFeat.Next

    ' Step 3 - selecting topology errors

    While Not ((topoError = eErrorFeat.Next) Is Nothing)
        topologyExt.AddActiveError(topoError, esriTEEventHint.esriTENone)
    End While


In the while sentence: While Not ((topoError = eErrorFeat.Next) Is Nothing)

An error indicates:

Operator '=' is not defined for types 'ESRI.ArcGIS.Geodatabase.ITopologyErrorFeature' and 'ESRI.Geodatabase.ITopologyErrorFeature'. Use 'Is' operator to compare two reference types.

When I change "=" to "Is", another error indicates:

'Is' operator does not accept operands of Type 'Boolean'. Operands must be reference or nullable types.

So I don't know how to define the equals operator of 2 'ESRI.ArcGIS.Geodatabase.ITopologyErrorFeature'. Thanks in advance.


Try this syntax:

topoError = eErrorFeat.Next
Do While Not (topoError Is Nothing)
    topologyExt.AddActiveError(topoError, esriTEEventHint.esriTENone)
    topoError = eErrorFeat.Next

You may want to confirm that eErrorFeat is not actually Nothing?

  • Hi Hornbydd, thanks. in fact I want to get the topology error list. – ppLily Aug 11 '14 at 1:20

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