Commands

The RadMap control exposes a Commands property that allows you to register custom commands that are triggered through the map behaviors. The commands have an Id property that defines which behavior will trigger the execution, and the default action of the command. The type of the parameter passed to the command also depends on the Id. Here are the available values:

• Unknown: The command is not familiar to the RadMap and it will not execute. This is the default value.
• ViewChanged: The command is associated with a change either in the Center or ZoomLevel (or both) properties of the RadMap. It is triggered by a user input through the MapPanAndZoomBehavior. The parameter passed to the command is of type ViewChangedContext and exposes the following properties:
  • NewCenter (Location): Gets or sets a value that will be set as the new Center of the RadMap.
  • NewZoomLevel (double): Gets or sets a value that will be set as the new ZoomLevel of the RadMap.
  • PreviousCenter (Location): Gets the previous Center value of the RadMap.
  • PreviousZoomLevel (double): Gets the previous ZoomLevel value of the RadMap.
  • ShapeSelectionChanged: The command is associated with a change in the SelectedShapes property of a MapShapeSelectionBehavior instance. The parameter passed to the command is of type SelectionChangedEventArgs and exposes the following properties:
  • AddedItems
  • RemovedItems
• ShapeLayerSourceChanged: The command is that is triggered when an IShapeDataSource instance is specified as a source to a MapShapeLayer and the IShapeDataSource.Shapes are prepared. The parameter passed to the command is the MapShapeLayer instance.

If no custom commands are defined, then the default ones will be used. The custom behaviors have higher priority than the default ones.

When you add a custom command to the RadMap, make sure that you have added the behavior that triggers the execution of this type of command in the Behaviors collection of the map.

Example

Here is an example that demonstrates how to create a custom command that limits the ZoomFactor of the RadMap to 2. There are two ways to do that:

• You can override the CanExecute method of the command to allow execution only if the ZoomFactor is bigger than 2.
• You can override the Execute method of the command to rollback the ZoomFactor and Center properties if the ZoomFactor is bigger than 2.

To demonstrate the two cases, we will create a custom command class for each one. The command classes should inherit from the MapCommand class.

public class LimitZoomCommand1 : MapCommand
{
    public LimitZoomCommand1()
    {
        this.Id = CommandId.ViewChanged;
    }

    public override bool CanExecute(object parameter)
    {
        var context = parameter as ViewChangedContext;
        if (context.NewZoomLevel < 2)
        {
            return true;
        }

        return false;
    }
}

public class LimitZoomCommand2 : MapCommand
{
    public LimitZoomCommand2()
    {
        this.Id = CommandId.ViewChanged;
    }

    public override bool CanExecute(object parameter)
    {
        return true;
    }

    public override void Execute(object parameter)
    {
        base.Execute(parameter);
        var context = parameter as ViewChangedContext;
        if (context.NewZoomLevel > 2)
        {
            context.NewZoomLevel = context.PreviousZoomLevel;
            context.NewCenter = context.PreviousCenter;
        }

        this.Owner.CommandService.ExecuteDefaultCommand(CommandId.ViewChanged, context);
    }
}

Then we have to add an instance of our custom command in the Commands collection of the RadMap

<telerikMap:RadMap>
    <telerikMap:RadMap.Behaviors>
        <telerikMap:MapPanAndZoomBehavior/>
    </telerikMap:RadMap.Behaviors>

    <telerikMap:RadMap.Commands>
        <local:LimitZoomCommand1/>
    </telerikMap:RadMap.Commands>

    <telerikMap:RadMap.Layers>
        <!-- add layers to the map -->
    </telerikMap:RadMap.Layers>
</telerikMap:RadMap>

Alternatively you can use LimitZoomCommand2 command instead of LimitZoomCommand1.

See Also

• Behaviors Overview