topic Re: Graphics Layer with custom markers not showing.... in ArcGIS API for Silverlight Questions

Graphics Layer with custom markers not showing....

KevinKing — Thu, 16 Jun 2011 14:35:04 GMT

Hey,

I'm just starting with ESRI, and have been using Silverlight with Bing Maps for some time now. I'm trying to add MapPoint elements to a graphics layer within the ESRI map, and at one point I was successful with this.

I haven't been able to get the dots to show up ever since I tried setting the Extent of my map based on an area defined in an Envelope. Here are some code segments of what I'm doing, and perhaps someone will see what I am not.

Here is the XAML markup:

            <esri:Map Name="MyMap" Width="800" Height="600" >
                <esri:Map.Layers>
                    <esri:ArcGISTiledMapServiceLayer ID="BaseLayer" x:Name="BaseLayer" 
              Url="http://server.arcgisonline.com/arcgis/services/World_Street_Map/MapServer" />
                    <esri:GraphicsLayer ID="DataLayer" />
                </esri:Map.Layers>                
            </esri:Map>

Here is where I add the graphics and set the extents. The "data" object is what i'm receiving back from my web service call, so pretend that looks like a real data collection with each item having a Latitude and Longitude. Also, the "center" map point is where I want to center the map, which comes back from the web service as well.

            GraphicsLayer dataLayer = DUMap.Layers["DataLayer"] as GraphicsLayer;
            dataLayer.Graphics.Clear();
            if (dataLayer != null)
            {
                List<object> data = new List<object>();
                foreach (object o in data)
                {
                    MapPoint point = new MapPoint(o.Longitude, o.Latitude);
                    Graphic graphic = new Graphic();
                    graphic.Symbol = new SimpleMarkerSymbol();
                    graphic.Geometry = ESRI.ArcGIS.Client.Bing.Transform.GeographicToWebMercator(point);
                    dataLayer.Graphics.Add(graphic);
 
                }
                MapPoint center = new MapPoint(data.center_long, data.center_lat);
                ESRI.ArcGIS.Client.Geometry.Geometry g = ESRI.ArcGIS.Client.Bing.Transform.GeographicToWebMercator(center);
                g.SpatialReference = DUMap.SpatialReference;
                double width = 4;
                Envelope envelope = new Envelope()
                {
                    XMin = center.X - width,
                    YMin = center.Y - width,
                    XMax = center.X + width,
                    YMax = center.Y + width,
                    SpatialReference = MyMap.SpatialReference
                };
                MyMap.Extent = envelope;
                dataLayer.Refresh();
            }

If I've left anything out that is important, please let me know. I had the dots showing on the map before I tried messing with the extent by adding a custom envelope, so that's where I'm guessing I'm going wrong.

Thanks so much!

Kevin

Re: Graphics Layer with custom markers not showing....

JenniferNery — Thu, 16 Jun 2011 15:48:53 GMT

You are setting the map's extent to zoom to the layer's extent? Without these lines of code, do you see any features on your map at all?

   MapPoint center = new MapPoint(data.center_long, data.center_lat);
                ESRI.ArcGIS.Client.Geometry.Geometry g = ESRI.ArcGIS.Client.Bing.Transform.GeographicToWebMercator(center);
                g.SpatialReference = DUMap.SpatialReference;
                double width = 4;
                Envelope envelope = new Envelope()
                {
                    XMin = center.X - width,
                    YMin = center.Y - width,
                    XMax = center.X + width,
                    YMax = center.Y + width,
                    SpatialReference = MyMap.SpatialReference
                };
                MyMap.Extent = envelope;

Are the graphics' geometry in the same spatial reference as the map? If not, you might need to call project: http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#Project

Re: Graphics Layer with custom markers not showing....

KevinKing — Thu, 16 Jun 2011 16:38:52 GMT

No, the markers do not show up at all. I added this line:

graphic.Geometry.SpatialReference = MyMap.SpatialReference;

However, that didn't help anything.

At one point I was able to add the markers to the map... ahhh!

Thanks for your reply!

Re: Graphics Layer with custom markers not showing....

KevinKing — Thu, 16 Jun 2011 17:06:41 GMT

I do notice that the Spatial Reference for my DataLayer (which is a graphics layer) is null.

I cannot set it in code, but I'm reading that it should use the spacial reference of the layers added before it (Tiled layer)?

Is this a problem with my tiled layer?

Does anyone have an example of using projection to set the spacial reference of a graphics layer?

Thanks!