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void CreatePolylineFromExistingGeometries(ESRI.ArcGIS.Geometry.IPolygon pPolygon1, ESRI.ArcGIS.Geometry.IPolygon pPolygon2) { //Build a new polyline by intersecting two existing polygons. ESRI.ArcGIS.Geometry.ITopologicalOperator2 pTopoOp2 = pPolygon1 as ITopologicalOperator2; //Simplify. pTopoOp2.IsKnownSimple_2 = false; pTopoOp2.Simplify(); ESRI.ArcGIS.Geometry.IPolyline pPoly = pTopoOp2.Intersect(pPolygon2, ESRI.ArcGIS.Geometry.esriGeometryDimension.esriGeometry1Dimension) as IPolyline; //pPoly is the new generated polyline. }