Get segment of polyline between 2 points

[GaryBushek]

Hi. I have 2 points that were obtained from intersecting street 2 with street 1 and then street 3 with street 1.  Now I want to get the segment of street 1 that falls between those 2 points.  Is there an easy way to do this in the silverlight API?  I'm looking for some good ideas on which direction to go; whether there are geometry service utilities in the API to handle this or if there are toolbox tools I should be utilizing within a custom geoprocessing service. Any guidance is greatly appreciated.  The old code for this process was written in 9.1 ADF/ArcObjects using IPath.QueryPointAndDistance() and IPath.GetSubCurve() and somehow I need to accomplish the same thing in the Silverlight API.  I included the old code below simply to show the complexity that was being handled in the old code written several years ago.

Thanks, Gary



The old code looks like this:

            ...Pts is an array that typically will hold 2 points found by interesting street 2 with street 1 and street 3 with street 1.
            ...pTopo is the street 1 geometry
            ...pT is the final polyline segment returned

            Dim pLine As IGeometryCollection = CType(glb.SC.CreateObject("esriGeometry.Polyline"), IGeometryCollection)
            'Now we have all the points. Find the points of the segment lines.
            Dim PathNum(Pts.Count) As Integer
            Dim Dist(Pts.Count) As Double
            For I = 0 To Pts.Count - 1
                PathNum(I) = -1
            Next

            Dim pPoint As IPoint = CType(glb.SC.CreateObject("esriGeometry.Point"), IPoint)
            WebObj.ManageLifetime(pPoint)
            Dim GeoCol As IGeometryCollection = CType(pTopo, IGeometryCollection)
            Dim path As IPath
            Dim DistAlongCurve As Double
            Dim DistanceFromCurve As Double
            Dim RightSide As Boolean

            For I = 0 To GeoCol.GeometryCount - 1
                path = CType(GeoCol.Geometry(I), IPath)

                For J = 0 To Pts.Count - 1
                    If PathNum(J) = -1 Then
                        path.QueryPointAndDistance(esriSegmentExtension.esriNoExtension, CType(Pts(J), IPoint), False, pPoint, DistAlongCurve, DistanceFromCurve, RightSide)
                        If Math.Abs(DistanceFromCurve) < 10 Then
                            PathNum(J) = I
                            Dist(J) = DistAlongCurve
                        End If
                    End If
                Next

                'Find start and end point on this segment
                Dim StartPt As IPoint = Nothing
                Dim EndPt As IPoint = Nothing
                Dim MinDist As Double = 99999999
                Dim MaxDist As Double = -1
                For J = 0 To Pts.Count - 1
                    If PathNum(J) = I Then
                        If Dist(J) < MinDist Then
                            StartPt = CType(Pts(J), IPoint)
                            MinDist = Dist(J)
                        End If
                        If Dist(J) > MaxDist Then
                            EndPt = CType(Pts(J), IPoint)
                            MaxDist = Dist(J)
                        End If
                    End If
                Next

                If MinDist < MaxDist Then
                    'A peice of segment found
                    Dim pL3 As ICurve = CType(glb.SC.CreateObject("esriGeometry.Polyline"), ICurve)
                    WebObj.ManageLifetime(pL3)

                    path.GetSubcurve(MinDist, MaxDist, False, pL3)
                    pLine.AddGeometry(pL3)
                End If
            Next


            'When we exit this method, we do not need the complete shape, so dispose it
            WebObj.ManageLifetime(pTopo)

            'If pLine has something return it, otherwise return nothing
            Dim pT As ITopologicalOperator = CType(pLine, ITopologicalOperator)
            pT.Simplify()
            Dim pL4 As IPolyline = CType(pLine, IPolyline)
            If pL4.IsEmpty Then
                WebObj.ManageLifetime(pLine)
                Return Nothing
            End If
            pL4.SpatialReference = glb.MapInfo.SpatialReference

            Return pT