InformationDataProviderBase.LayerItemsGenerating Event

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

Namespace: DevExpress.Xpf.Map

Assembly: DevExpress.Xpf.Map.v19.1.dll

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 calculate a route between several waypoints and change the appearance of a route path using the Microsoft Bing Route web service. 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.

• 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 route path appearance, handle the InformationDataProviderBase.LayerItemsGenerating event and modify the MapPushpin.Text property of each MapPushpin.

  Note that map pushpins for waypoints are generated automatically and the LayerItemsGenerating event occurs because the InformationDataProviderBase.GenerateLayerItems property value is true by default.

Note

If you run the application, and see a window with the following error message: ”The specified Bing Maps key is invalid. To create a developer account, refer to https://www.microsoft.com/en-us/maps/create-a-bing-maps-key”, refer to the following tutorial: How to: Get a Bing Maps Key.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-connect-a-map-control-to-a-bing-route-web-service-e4159.

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
    Next item
End Sub

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 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();
    }
}

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.

C#

how-to-connect-a-map-control-to-a-bing-route-web-service-e4159/CS/MainWindow.xaml#L23

                               BingKey="{Binding Source={StaticResource YourBingKey}}"
                               LayerItemsGenerating="routeProvider_LayerItemsGenerating"/>
</dxm:InformationLayer.DataProvider>

how-to-programmatically-search-using-the-bing-map-search-service-e4238/CS/DXMapExample/MainWindow.xaml#L33

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

how-to-get-routes-to-the-destination-point-using-the-bing-map-route-data-service-e4250/CS/CalculateRoutesFromMajorRoads/MainWindow.xaml#L102

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