topic Re: Buffer around a point with button in ArcGIS API for Silverlight Questions

Buffer around a point with button

SchoolRadius — Mon, 04 Apr 2011 02:03:46 GMT

Hi, I'm trying to create a buffer around a school and i only want the buffer to come out when i click a button from the pop up menu of the school, I already have the pop up menu and the map, what i need is to know how to capture the x,y coordinates of the school and how to subsequently draw a buffer around the school. Any ideas?

Re: Buffer around a point with button

DominiqueBroux — Mon, 04 Apr 2011 13:23:15 GMT

i need is to know how to capture the x,y coordinates of the school

If you have a popup menu of the school, it probably means that the school is a graphic. You can get the x and y of a graphic by using the geometry:
x = (graphic.Geometry as MapPoint).X;
y = (graphic.Geometry as MapPoint).Y;

how to subsequently draw a buffer around the school

You can add a graphic having a Polygon geometry initialized to a circle around the school (circle to approximate by a polyline around the school).

Re: Buffer around a point with button

SchoolRadius — Tue, 05 Apr 2011 00:57:41 GMT

Thanks for the pointers Dominque but i still do not really understand it fully, these are my codes for the button, there are errors when I key it in, any ideas where I went wrong or what am I missing?

protected void Buffer2Button(object sender, RoutedEventArgs e)
        {
            x = (graphic.Geometry as MapPoint).X;
            y = (graphic.Geometry as MapPoint).Y;
            GraphicsLayer graphicsLayer = MyMap.Layers["MyGraphicsLayer_Buffer"] as GraphicsLayer;
            graphicsLayer.ClearGraphics();

            e.MapPoint.SpatialReference = MyMap.SpatialReference;
            Graphic graphic = new ESRI.ArcGIS.Client.Graphic()
            {
                Geometry = e.MapPoint,
                Symbol = LayoutRoot.Resources["DefaultBufferSymbol"] as ESRI.ArcGIS.Client.Symbols.Symbol
            };
            graphic.SetZIndex(1);
            graphicsLayer.Graphics.Add(graphic);

            GeometryService geometryService =
            new GeometryService ("http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer");
            geometryService.BufferCompleted += GeometryService_BufferCompleted;
            geometryService.Failed += GeometryService_Failed;

          BufferParameters bufferParams = new BufferParameters()
          {
              Unit = LinearUnit.Kilometer,
              BufferSpatialReference = new SpatialReference(4326),
              OutSpatialReference = MyMap.SpatialReference
          };
          bufferParams.Features.Add(graphic);
          bufferParams.Distances.Add(2);

          geometryService.BufferAsync(bufferParams);
      }

Re: Buffer around a point with button

SchoolRadius — Tue, 05 Apr 2011 01:47:46 GMT

Also when I enter this into my codes, I keep getting an error that says "the name graphic does not exist in the current context"

string axisX = (graphic.Geometry as MapPoint).X;
string axisY = (graphic.Geometry as MapPoint).Y;

Re: Buffer around a point with button

DominiqueBroux — Tue, 05 Apr 2011 07:14:50 GMT

I was supposing that you were using a GraphicsLayer or FeatureLayer to display your school.

Is it the case?

If it's the case, the graphic variable have to be initialized with the graphic of your school (either by an user interaction such as a click or by code filtering the graphics of your graphicslayer by attribute).

Re: Buffer around a point with button

SchoolRadius — Tue, 05 Apr 2011 08:43:25 GMT

I am using a graphicLayer for my school and it is initialized with a button but how do I carry on and draw a buffer?

p.s. sorry I'm quite lost, I'm new to this