GraphicsLayer Spatial Reference

KeremCelik

Hi,

I want to add a graphics layer in Map. But this layer is lack of Spatial Reference. I cannot specify the spatial reference, because it's property is read only(just get is implemented in the API).

Here is xaml (It is generated when I create an ESRI SL Application in Visual Studio)

<esri:Map x:Name="Map" Background="White">
    ....
    ....
      <esri:Map.Layers>
             <esri:ArcGISTiledMapServiceLayer ID="BaseLayer"
 Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"/>
      </esri:Map.Layers>
</esri:Map>

I want to create Graphics Layer with the following code behind C# code

public GraphicsLayer CreatePointGraphicLayer(string ID,
            SpatialReference spatial_reference,
            List<double> x_list,
            List<double> y_list,
            List<string> fields,
            List<string[]> other_fields_values)
{
 GraphicsLayer graphics_layer = new GraphicsLayer();
 graphics_layer.ID = ID;

 SimpleMarkerSymbol simple_marker_symbol = new SimpleMarkerSymbol();
 simple_marker_symbol.Color = new SolidColorBrush(Colors.Red);

 for (int i = 0; i < x_list.Count; i++)
 {
  Graphic graphic = new Graphic()
  {
   Symbol = simple_marker_symbol,
   Geometry = new MapPoint(x_list, y_list, spatial_reference)
  };

  for (int j = 0; j < fields.Count; j++)
  {
   graphic.Attributes[fields] = other_fields_values;
  }

  graphics_layer.Graphics.Add(graphic);
 }

 return graphics_layer;
}

The code above create the graphics layer and when I put it into Map with the following lines of code, I can see the created graphics but lack of spatial reference.

GraphicsLayer g_layer = CreatePointGraphicLayer(....) //I omit this part
Map.Layers.Add(g_layer); 

How can I use spatial reference in graphics layer.

Thanks in advance.
Kerem.

ScottKutz

Mark,

Just to note ... the information in the following thread provided insights that may be helpful:

https://community.esri.com/thread/117206

Following that example, the fragment below shows a class derived from GraphicsLayer that overrides the OnInitializeGraphicsLayerRequestedAsync() method.

---------------------

public class MyGraphicsLayer : GraphicsLayer
{
  private SpatialReference _layerSpatialReference = null;

  public MyGraphicsLayer(SpatialReference layerSpatialReference)
  {
    // Capture the specified spatial reference so it is available
    // for use in the OnInitializeGraphicsLayerRequestedAsync() override.
    _layerSpatialReference = layerSpatialReference;
  }

  protected override Task<GraphicsLayerInitializationInfo> OnInitializeGraphicsLayerRequestedAsync()
  {
    return Task.FromResult(
      new GraphicsLayerInitializationInfo() { PreferredSpatialReference = _layerSpatialReference }
      );
  }
}

-------------------

The fragment below demonstrates using the derived class (plus .InitializeAsynch) to assign the Spatial Reference:

--------------------

// Source of the graphic data is a FeatureSet loaded from the content of a *.json file.
// The returned FeatureSet has its SpatialReference property set.

// The intent is to assign that SpatialReference to the graphics layer prior to populating the layer.

string jsonFileContent = (... previously read from a *.json file ...)
FeatureSet featureSet = FeatureSet.FromJson(jsonFileContent);

MyGraphicsLayer graphicsLayer = new MyGraphicsLayer(featureSet.SpatialReference);

// Execution of the .InitializeAsync() call does transfer control into

// the OnInitializeGraphicsLayerRequestedAsync() override above.

// The effect is to assign the spatial reference to the graphics layer.

await graphicsLayer.InitializeAsync();

---------------------

  While the above approach seems to achieve the objective, it does require more code than one might expect (at least, in my opinion, it seems there could be a more straightforward technique for assigning a Spatial Reference to a graphics layer).

Scott