Suggestion for GraphisLayer.GraphicsSource property

wangzhifang

Hi all,
GraphicsSource is very good idea for binding using in MVVM. But I found some issues on this property and thought it worth to be improved for GraphicsSource.
For instance, I have a GraphicsLayer on Map control which ID="GLayer", and a ObservableCollection<Graphic> which stores my Graphics. Manipulating on ObservableCollection<Graphic> such as remove and add can be reflected to GraphicsLayer and then on Map:

_graphics = new ObservableCollection<Graphic>(some graphics);
(Map1.Layers["GLayer"] as GraphicsLayer).GraphicsSource = _graphics;
...
_graphics.Clear();
foreach (Graphic g in new ObservableCollection<Graphic>(some new graphics)
                _graphics.Add(g);

However, directly set the _graphics just not working:

_graphics = new ObservableCollection<Graphic>(some new graphics);//just not working as expected.

When directly setting _graphics as above, nothing happend on Map.

I expected below directly set the _graphics just working as previously. Don't know am I right?

TraceyRichvalsky

Hi James,
It's been a while since I've looked at this part of my project but here is what I ended up doing.  Also, I don't think I was actually getting an error - I think it was just that nothing happened on the updates.  Hopefully this helps you.  I found this in another post from an ESRI developer in a forum:  "While your Map can inherit the DataContext of your UserControl, GraphicsLayer will not. GraphicsLayer, unlike Map or any other UIElement, does not have a DataContext and will therefore fail to resolve this type of Binding."  So what I did was to define the map and all of its components in the C# as follows (some of my names are different than my original post b/c that was a prototype - I did have some other issues when I integrated the prototype so I'm hoping that I'm answering your question and not a different problem I had):

C# that replaces the .xaml code in the View - this is in the ViewModel of the piece of my project that creates a map report

Map myMap = new Map();
                    myMap.WrapAround = true;
                    myMap.ZoomFactor = 1.2;
                    //street map
                    ArcGISTiledMapServiceLayer sl = new ArcGISTiledMapServiceLayer();
                    sl.Url = "http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer";
                    myMap.Layers.Add(sl);

                    //add the points layer to the map
                    List<string> pointsMapTipLabels = new List<string>() { "Info" };
                    myMap.Layers.Add(((Geospatial_ViewModel)tileViewModel.ContentViewModel).addGraphicsLayer("MyPointsList", "IsPointsLayerVisible", pointsMapTipLabels));
                    tileContentView.Content = myMap;

Here is the addGraphicsLayer() function (this is in the map ViewModel):

//This adds a layer containing WACs to the map; pass in the name of the wac list and
        // the name of the boolean that controls visibility for binding
        public GraphicsLayer addGraphicsLayer(string list, string isGridVis, List<string> mapTips)
        {
            GraphicsLayer layer = new GraphicsLayer();
            //list binding            
            Binding listBinding = new Binding(list);
            listBinding.Source = this;
            listBinding.Mode = System.Windows.Data.BindingMode.TwoWay;
            BindingOperations.SetBinding(layer, GraphicsLayer.GraphicsProperty, listBinding);

            //list visibility binding - controls whether thepoints are visible
            Binding listVisBinding = new Binding(isGridVis);
            listVisBinding.Source = this;
            listVisBinding.Mode = BindingMode.TwoWay;
            BindingOperations.SetBinding(layer, GraphicsLayer.VisibleProperty, listVisBinding);

            //map tips
            MapTip mt = new MapTip();
            Grid mtgrid = new Grid();
            Color lightYellow = getColorFromHexString("FFFFFFE0");
            mtgrid.Background = new SolidColorBrush(lightYellow);
            System.Windows.Thickness thOne = new Thickness();
            thOne.Bottom = thOne.Left = thOne.Right = thOne.Top = 1;
            mtgrid.Children.Add(new Border() { BorderBrush = new SolidColorBrush(Colors.Black), BorderThickness = thOne });
            StackPanel mtpanel = new StackPanel();
            System.Windows.Thickness thFive = new Thickness();
            thFive.Bottom = thFive.Left = thFive.Right = thFive.Top = 5;
            mtpanel.Margin = thFive;
            mtpanel.Orientation = Orientation.Vertical;
            mtgrid.Children.Add(mtpanel);

            foreach (string tip in mapTips)
            {
                mtpanel.Children.Add(createMapTipTextBlock(tip));
            }
            layer.MapTip = mtgrid;

            return layer;
        }

This is all I have in the map View (.xaml file).  I am using a ComponentOne tile to display different types of reports.  In most cases, the content of the TileItem gets set to the View.  This works when my report is a chart but when the report is the ESRI map, it does not so there is basically nothing in the map's .xaml View file.

    <UserControl.Resources>
        <esriConverters:DictionaryConverter x:Key="MyDictionaryConverter" />
    </UserControl.Resources>

    <Grid x:Name="LayoutRoot"
          Background="White">
    </Grid>
</UserControl>

This is the list of points that is used for the binding (in the map ViewModel):

        private GraphicCollection myPointsList;
        public GraphicCollection MyPointsList
        {
            get { return myPointsList; }
            set
            {
                myPointsList = value;
                RaisePropertyChanged("MyPointsList");                                
            }
        }

Then in the map Model, when my query results come back, I update MyPointsList:

GraphicCollection glist = new GraphicCollection();
                SpatialReference sref = new SpatialReference(4326);
                SolidColorBrush pointColor;

                double prevLat = 0.0;
                double prevLon = 0.0;
                double maxValue = 0.0;

                //loop through points returned
                for (int x = 0; x < e.Result.geoData.Count(); x++)
                {
                    double lat = e.Result.geoData.Latitude;
                    double lon = e.Result.geoData.Longitude;
                    string name = e.Result.Name;
                    double value = e.Result.MeasureValues;

                        Graphic g = new Graphic()
                            {
                                Geometry = new MapPoint(lon, lat, sref)
                            };

                        g.Symbol = new SimpleMarkerSymbol()
                        {
                            Color = new SolidColorBrush(Colors.Red),
                            Size = 18,
                            Style = SimpleMarkerSymbol.SimpleMarkerStyle.Circle
                        };

                        //mouse over data
                        g.Attributes.Add("Info", name + ": " + value.ToString() + " " + viewModel.MeasureSelected.Name);

                        glist.Add(g);                    

                } //end for each point
                viewModel.MyPointsList = glist;

Hopefully this helps and isn't too confusing!  I tried to remove the non-relevant code so you could see what the binding is doing easliy.  Good luck!