Graphics Not Updating in MapView from ViewModel GraphicsOverlay - wpf

Question

I am developing an application with ArcGIS Runtime SDK for .Net and following the MVVM Pattern, in my ViewModel I have an ObservableCollection of GraphicsOverlay that I have binded to the MapView in my View, now when I add a new GraphicsOverlay to the ObservableCollection and add Graphics in it, graphics are not reflection in the View,
I have implemented INotifyPropertyChanged and all other things are working fine with the ViewModel
public class MapViewModel : BaseViewModel
{
private Map map;
public Map Map
{
get { return this.map; }
set { this.map = value; }
}
public ObservableCollection<GraphicsOverlay> GraphicsOverlays { get; set; }
public MapViewModel()
{
GraphicsOverlays = new ObservableCollection<GraphicsOverlay>();
}
And in my Method that is called by any event
public void UpdateMarker(MapPoint point)
{
GraphicsOverlays[0].Graphics.Clear();
// Create a symbol to symbolize the point
SimpleMarkerSymbol symbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.X, System.Drawing.Color.Yellow, 20);
// Create the graphic
Graphic symbolGraphic = new Graphic(point, symbol);
// Add the graphic to the graphics overlay
var newGraphicsOverlay=new GraphicsOverlay();
GraphicsOverlays[0].Graphics.Add(symbolGraphic);
}
And in my View I have
<esri:MapView x:Name="MyMapView" Grid.Column="0" DataContext="
{StaticResource MapVM}" GraphicsOverlays="{Binding GraphicsOverlays}" Map="
{Binding Map}" Cursor="{Binding MapViewCursor}">
I am unable to find any sample that does exactly this, so how to do this, I am new to arcGIS, Thanks in advance.
Update
I have updated the UpdateMarker Method like this
public void UpdateMarker(MapPoint point)
{
GraphicsOverlays[0].Graphics.Clear();
// Create a symbol to symbolize the point
SimpleMarkerSymbol symbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.X, System.Drawing.Color.Yellow, 20);
// Create the graphic
Graphic symbolGraphic = new Graphic(point, symbol);
// Add the graphic to the graphics overlay
var newGraphicsOverlay = new GraphicsOverlay();
newGraphicsOverlay.Graphics.Add(symbolGraphic);
GraphicsOverlays[0] = newGraphicsOverlay;
}
But still the symbol is not showing on the map.

Answer 1

I think you have to use a GraphicsOverlayCollection instead of an ObservableCollection as MapView.GraphicOverlays is a GraphicsOverlayCollection and not an ObservableCollection. Something like
public GraphicsOverlayCollection<GraphicsOverlay> GraphicsOverlays { get; set; }