InformationDataProviderBase.LayerItemsGenerating Event

Occurs when a data provider starts generating map items for a layer.

Namespace: DevExpress.Xpf.Map

Assembly: DevExpress.Xpf.Map.v23.2.dll

NuGet Package: DevExpress.Wpf.Map

Declaration

C#

public event LayerItemsGeneratingEventHandler LayerItemsGenerating

VB.NET

Public Event LayerItemsGenerating As LayerItemsGeneratingEventHandler

Event Data

The LayerItemsGenerating event's data class is LayerItemsGeneratingEventArgs. The following properties provide information specific to this event:

Property	Description
Cancelled	Gets a value indicating whether an asynchronous operation has been canceled. Inherited from AsyncCompletedEventArgs.
Error	Gets a value indicating which error occurred during an asynchronous operation. Inherited from AsyncCompletedEventArgs.
Items	Returns all the items generated for the layer.
UserState	Gets the unique identifier for the asynchronous task. Inherited from AsyncCompletedEventArgs.

The event data class exposes the following methods:

Method	Description
RaiseExceptionIfNecessary()	Raises a user-supplied exception if an asynchronous operation failed. Inherited from AsyncCompletedEventArgs.

Example

This example demonstrates how to use the Microsoft Bing Route web service to calculate a route between multiple waypoints and how to customize the appearance of the resulting route path.

To accomplish this, do the following:

• Create an InformationLayer object and add it to the MapControl.Layers collection.

• Create a BingRouteDataProvider object and assign it to the InformationLayer.DataProvider property. Specify the provider’s key. For more information, refer to the following help topic: How to: Get a Bing Maps Key.

• To calculate a route, call the BingRouteDataProvider.CalculateRoute method and pass a list of waypoints as its argument.

  Note

  The BingRouteDataProvider.CalculateRoute method calculates the route based on less than 265 RouteWaypoint objects.

• To customize the resulting route path’s appearance, handle the InformationDataProviderBase.LayerItemsGenerating event and configure appearance of the items contained in the event arguments (the Itemsproperty). This example shows how to specify text displayed in generated pushpins and define colors used to draw the path between pushpins.

  The Map Control generates map pushpins for waypoints and raises the LayerItemsGenerating event only when the InformationDataProviderBase.GenerateLayerItems property value is true. If the GenerateLayerItems property value is false, you can create pushpins or other map vector items based on your waypoints in the BingRouteDataProvider.RouteCalculated event handler.

MainWindow.xaml

<dxm:InformationLayer EnableHighlighting="False">
    <dxm:InformationLayer.DataProvider>
        <dxm:BingRouteDataProvider x:Name="routeProvider" 
                                   BingKey="{Binding Source={StaticResource YourBingKey}}"
                                   LayerItemsGenerating="routeProvider_LayerItemsGenerating"/>
    </dxm:InformationLayer.DataProvider>
</dxm:InformationLayer>

MainWindow.xaml.cs

public partial class MainWindow : Window {

    public MainWindow() {
        InitializeComponent();

        // Create three waypoints and add them to a route waypoints list. 
        List<RouteWaypoint> waypoints = new List<RouteWaypoint>();
        waypoints.Add(new RouteWaypoint("New York", new GeoPoint(41.145556, -73.995)));
        waypoints.Add(new RouteWaypoint("Oklahoma", new GeoPoint(36.131389, -95.937222)));
        waypoints.Add(new RouteWaypoint("Las Vegas", new GeoPoint(36.175, -115.136389)));

        routeProvider.CalculateRoute(waypoints);
    }

    private void routeProvider_LayerItemsGenerating(object sender, LayerItemsGeneratingEventArgs args) {
        char letter = 'A';
        foreach (MapItem item in args.Items) {
            MapPushpin pushpin = item as MapPushpin;
            if (pushpin != null)
                pushpin.Text = letter++.ToString();
            MapPolyline line = item as MapPolyline;
            if (line != null) {
                line.Fill = Brushes.Red;
                line.Stroke = Brushes.Red;
            }
        }

        map.ZoomToFit(args.Items);
    }
}

MainWindow.xaml.vb

        Public Sub New()
            InitializeComponent()

            ' Create three waypoints and add them to a route waypoints list. 
            Dim waypoints As New List(Of RouteWaypoint)()
            waypoints.Add(New RouteWaypoint("New York", New GeoPoint(41.145556, -73.995)))
            waypoints.Add(New RouteWaypoint("Oklahoma", New GeoPoint(36.131389, -95.937222)))
            waypoints.Add(New RouteWaypoint("Las Vegas", New GeoPoint(36.175, -115.136389)))

            routeProvider.CalculateRoute(waypoints)
        End Sub

        Private Sub routeProvider_LayerItemsGenerating(ByVal sender As Object, ByVal args As LayerItemsGeneratingEventArgs)
            Dim letter As Char = "A"c

            For Each item As MapItem In args.Items
                Dim pushpin As MapPushpin = TryCast(item, MapPushpin)
                If pushpin IsNot Nothing Then
                    pushpin.Text = letter.ToString()
                    letter = ChrW(AscW(letter) + 1)
                End If
                Dim line As MapPolyline = TryCast(item, MapPolyline)
                If line IsNot Nothing Then
                    line.Fill = System.Windows.Media.Brushes.Red
                    line.Stroke = System.Windows.Media.Brushes.Red
                End If
            Next item
            map.ZoomToFit(args.Items)
        End Sub

Related GitHub Examples

The following code snippets (auto-collected from DevExpress Examples) contain references to the LayerItemsGenerating event.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

XAML

wpf-map-programmatically-search-with-the-bing-map-search-service/CS/DXMapExample/MainWindow.xaml#L33

                            SearchCompleted="OnSearchCompleted"
                            LayerItemsGenerating="OnLayerItemsGenerating" />
<!--endregion #SearchCompleted-->

wpf-map-get-routes-to-the-destination-point-with-the-bing-map-route-data-service/CS/CalculateRoutesFromMajorRoads/MainWindow.xaml#L102

RouteCalculated="routeProvider_RouteCalculated"
LayerItemsGenerating="routeProvider_LayerItemsGenerating">
<dxm:BingRouteDataProvider.RouteStrokeStyle>