Bind graphics of GraphicLayer.[Bind GraphicCollection]

Question

hi,

I am using MVVM approuch and i need bind graphics of GraphicLayer i try:

<esri:GraphicsLayer ID="test" Graphics="{Binding graphics}" />

private GraphicCollection graphics;
        public GraphicCollection Graphics
        {
            get { 
                return graphics; 
            }
            set { 
                graphics = value;
                OnPropertyChanged("graphics");
            }
        }

the application hangs, not display nothing...anyone know how i can solve this issue?

JenniferNery · Answer

If you want to define the Binding in XAML, I don't see another way to do so without defining an instance of your ViewModel under Resource. If your ViewModel object looked like this public class MyViewModelObject : INotifyPropertyChanged { public MyViewModelObject() { Graphics = new GraphicCollection(); } private GraphicCollection graphics; public GraphicCollection Graphics { get { return graphics; } set { if (graphics != value) { graphics = value; OnPropertyChanged("Graphics"); } } } public event PropertyChangedEventHandler PropertyChanged; public void OnPropertyChanged(string property) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(property)); } You might be expecting that when you set your UserControl's DataContext to an instance of your ViewModel in code-behind like this: MyViewModelObject obj = new MyViewModelObject(); this.DataContext = obj; the following XAML-code would just work: Unfortunately, this is not the case. 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. If you wish to define the Binding in code-behind, these two are equivalent: XAML: Code-behind: MyViewModelObject obj = new MyViewModelObject(); GraphicsLayer layer = this.MyMap.Layers["MyGraphicsLayer"] as GraphicsLayer; System.Windows.Data.Binding binding = new System.Windows.Data.Binding("Graphics"); binding.Source = obj; binding.Mode = System.Windows.Data.BindingMode.TwoWay; System.Windows.Data.BindingOperations.SetBinding(layer, GraphicsLayer.GraphicsProperty, binding); Either way will let you modify the elements in your Map's GraphicsLayer. obj.Graphics.Add(new Graphic() { Geometry = new MapPoint(17, 15) });

BjørnarSundsbø · Answer

Hi

How do I get MyGraphics to contain the data from my ViewModels Graphics collection without monitoring changes to my viewmodel and adding them to the resource?

JenniferNery · Answer

You can define your GraphicCollection in Xaml under UserControl.Resources as such: and then create the binding to Graphics this way: Any changes to your GraphicCollection should affect the Graphics in your GraphicsLayer. Jennifer