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I am trying to develop arcgis 10.0 addin to update Z values of vertices of a selected line. Scenario: The tool scans all features in a given shape file and populates the list of features which has at least one vertex with a Z vlaue = 0. User then selects a feature from the list and clicks a button to update Z values to a given height - this last part does not work.

I have tried the following for updating Z values of a selected polyline feature with no luck:

    Dim pFeatureSelection As IFeatureSelection
            pFeatureSelection = pFLayer
            Dim pEnumID As IEnumIDs
            pEnumID = pFeatureSelection.SelectionSet.IDs
            Dim id As Long
            id = pEnumID.Next
            Dim pPointCollection As IPointCollection
            Dim pFeature As IFeature
            Do While Not id = -1
                pFeature = pFLayer.FeatureClass.GetFeature(id)
                pPointCollection = pFeature.Shape

                For lPnt = 0 To (pPointCollection.PointCount - 1)
                     SetZValueOnPoint(pPointCollection.Point(lPnt), Convert.ToDouble(txtZValue.Text))


                id = pEnumID.Next
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Thanks to Jeff's help we got the answer via the ArcGIS Discussion Forum:

Public Sub SetZValueOnPoint(ByVal point As ESRI.ArcGIS.Geometry.IPoint, ByVal zValue As System.Double)  

   If point Is Nothing OrElse point.IsEmpty Then  
   End If  

   Dim zAware As ESRI.ArcGIS.Geometry.IZAware = CType(point, ESRI.ArcGIS.Geometry.IZAware) ' Explicit Cast  
    zAware.ZAware = True  
    point.Z = zValue  

End Sub  
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If the desire is to make the polyline the same Z value all the way from start to finish then use IZ interface. This interface has a method SetConstantZ ( Double ZLevel ) which works for polygons and polylines that will set every vertex to the same Z value. This approach is much simpler than the GeometryCollection / PointCollection / IZaware approach which I have used previously to set individual Z values of points (i.e. all different).

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if IPolyLine was used. you have to only set zAware to true to solve this problem.

 Dim newSegCollection As ISegmentCollection = New Polyline
 Dim zAware As IZAware = CType(newSegCollection, IZAware)
 zAware.ZAware = True

then you can set z for FromPoint and ToPoint for each line in your IPolyLine shape.

and if you want to set same z for all lines in IPolyLine you can use IZ interface and SetConstantZ.

Dim iz As IZ2 = newSegCollection
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