get the points of a polygon

Question

I have a silverlight app where a user can draw a polygon on a map. I want a way to take the polygon and get the vertices. I can see how to get the envelope, but  not the actual points. In arcobjects you can convert an Ipolygon to an IpointCollection, but that does not seem possible in the SL API. Any direction would be appreciated.

BrianBehling · Answer

ESRI.ArcGIS.Client.Geometry.Polygon polygon =   (ESRI.ArcGIS.Client.Geometry.Polygon)graphic.Geometry;

int ringCount = polygon.Rings.Count;

for (int i = 0; i < ringCount; i++)
                    {
                        ESRI.ArcGIS.Client.Geometry.PointCollection pc = polygon.Rings;

foreach (ESRI.ArcGIS.Client.Geometry.MapPoint mp in pc)
                        {
                            MapPoint coordinates = new MapPoint(mp.X, mp.Y);

}
}

AvronPolakow · Answer

// This is how I do it: // Here's how I do it creating an XML type output (you can create whatever output you like) //////////////////////////////////////////////////////////////////////////// // ldblTolerance ; Tolerance for the removal of proximal points // lbXML ; XML output type: // true=short xml with attributes // false=long xml with tags // lbBrief ; Points in single tag //////////////////////////////////////////////////////////////////////////// StringBuilder lstrBuilder = new StringBuilder(); string [] LPad = ", , , , , , , , , , ".Split(','); double ldblTolerance = 0.000010; // For removal of proximal points. Usage: GetPoints() bool lbXML = true; bool lbBrief = true; lstrBuilder.Append(""); if (lGraphic.Geometry is ESRI.ArcGIS.Client.Geometry.Polygon) { ESRI.ArcGIS.Client.Geometry.Polygon lPolygon = (ESRI.ArcGIS.Client.Geometry.Polygon) lGraphic.Geometry; foreach (ESRI.ArcGIS.Client.Geometry.PointCollection lPoints in lPolygon.Rings) { lstrBuilder.Append(LPad[6] + " "); lstrBuilder = GetPoints(lstrBuilder, lbXML, lbBrief, ldblTolerance, LPad, lPoints); lstrBuilder.Append(LPad[6] + " "); } : : : return lstringBuilder.ToString(); ////////////////////////////////////////////////////////////////////// public static StringBuilder GetPoints(StringBuilder astrBuilder, bool abXML, bool abBrief, double adblTolerance, string[] LPad, ESRI.ArcGIS.Client.Geometry.PointCollection aPoints) { MapPoint lprevMapPoint = new MapPoint(); double ldblX, ldblY; lprevMapPoint.X = 0; lprevMapPoint.Y = 0; if (abBrief) { astrBuilder.Append(LPad[7] + ""); if (abXML && !abBrief) {astrBuilder.Append(" ");} } foreach(MapPoint lMapPoint in aPoints) { ldblX = Math.Round(lMapPoint.X, 6); // Math.Round(lMapPoint.X, 6); ldblY = Math.Round(lMapPoint.Y, 6); // Math.Round(lMapPoint.Y, 6); if (Math.Abs(ldblX - lprevMapPoint.X) > adblTolerance && Math.Abs(ldblY - lprevMapPoint.Y) > adblTolerance) { lprevMapPoint.X = ldblX; lprevMapPoint.Y = ldblY; // Brief if (abBrief) { if (abXML) {astrBuilder.Append(ldblX.ToString() + "," + ldblY.ToString() +",");} else { astrBuilder.Append(ldblX.ToString() + ","); astrBuilder.Append(ldblY.ToString() + " "); } } else { if (abXML) {astrBuilder.Append(LPad[7] + " ");} else { astrBuilder.Append(LPad[7] + " "); astrBuilder.Append(LPad[8] + "" + ldblX.ToString() + " "); astrBuilder.Append(LPad[8] + "" + ldblY.ToString() + " "); astrBuilder.Append(LPad[7] + " "); } } } } if (abBrief) { if (abXML && !abBrief) {astrBuilder.Append(" " + LPad[7]);} astrBuilder.Append(" "); } return astrBuilder; }

DominiqueBroux · Answer

Get the rings of the polygon, each ring is a collection of point.

For example, to get the points of the first ring of your polygon, you can use :ESRI.ArcGIS.Client.Geometry.PointCollection points = myPolygon.Rings[0];

/Dominique