Implement Custom Map Provider

If you need to consume a service which does not have a default provider, you can create a custom map provider and set it as the Provider property of the RadMap control.

MapProviderBase

The MapProviderBase is the base class for all map providers. Two widely-used implementations of the class are the TiledProvider and ImageProvider.

  • TiledProvider is a base class for map providers that show a map as a sequence of tiles (e.g. BingMaps, OpenStreetMap.

  • ImageProvider is a base class for providers that show a map as a single image (UriImageProvider).

Once you know the type of provider you require, you can create a custom class to inherit from it. In most cases this will be the TiledProvider class. In addition, you need to override the SpatialReference property - it returns the actual projection used by the provider and most often returns an instance of the MercatorProjection class.

Example 1: Create a custom TiledProvider

public class MyMapProvider : TiledProvider 
{ 
    /// <summary> 
    /// Initializes a new instance of the MyMapProvider class. 
    /// </summary> 
    public MyMapProvider() 
            : base() 
    { 
        MyMapSource source = new MyMapSource(); 
        this.MapSources.Add(source.UniqueId, source); 
    } 
 
    /// <summary> 
    /// Returns the SpatialReference for the map provider. 
    /// </summary> 
    public override ISpatialReference SpatialReference 
    { 
        get 
        { 
            return new MercatorProjection(); 
        } 
    } 
} 

The MyMapSource class is defined in Example 2.

MultiScaleTileSource

As seen in Example 1, the next requirement is to add instances of the abstract MultiScaleTileSource class to the provider's MapSources collection. The class exposes two useful properties:

  • RequestCredentials: Gets or sets credentials for downloading tiles.
  • WebHeaders: Gets or sets the headers used in the get requests made to the tile servers via System.Net.WebClient. This property was introduced with R2 2019 SP1.

The two default implementations of this abstract class are the TiledMapSource and the ImageMapSource.

  • TiledMapSource is a base class for map sources that return map tiles (that includes all BingMaps sources: aerial, road, birds eye, and all OpensStreetMap sources: Mapnik and Osmarenderer).

  • ImageMapSource is a base class for map sources that return a single map image.

When creating a custom map provider, you can choose one of these sources and override their methods depending on the specific map source type. Most implementations will require the following set of actions:

  • Override the Initialize method.

  • Override the GetTile method and existing custom logic should be moved here.

  • Call the RaiseInitializeCompleted method when the respective custom provider is initialized (in case of simple providers it is enough to call this method from the override Initialize method).

Example 2 demonstrates a possible implementation of a custom TiledMapSource.

Example 2: Create a custom TiledMapSource

public cs-class MyMapSource : TiledMapSource 
{ 
       /// <summary> 
       /// Initializes a new instance of the MyMapSource class. 
       /// </summary> 
       public MyMapSource() 
             : base(1, 20, 256, 256) 
       { 
       } 
 
       /// <summary> 
       /// Initialize provider. 
       /// </summary> 
       public override void Initialize() 
       { 
             // Raise provider initialized event. 
             this.RaiseIntializeCompleted(); 
       } 
 
       /// <summary> 
       /// Gets the image URI. 
       /// </summary> 
       /// <param name="tileLevel">Tile level.</param> 
       /// <param name="tilePositionX">Tile X.</param> 
       /// <param name="tilePositionY">Tile Y.</param> 
       /// <returns>URI of image.</returns> 
       protected override Uri GetTile(int tileLevel, int tilePositionX, int tilePositionY) 
       { 
             int zoomLevel = ConvertTileToZoomLevel(tileLevel); 
             // Prepare tile url somehow ... 
             string url = CustomHelper.GetTileUrl(tileLevel, tilePositionX, tilePositionY); 
             return new Uri(url); 
       } 
} 

Create an OpenStreetProvider Which Uses Https

A common requirement when using the RadMap control is to use the OpenStreetMap service over https. Examples 3-5 demonstrate how this can be achieved by creating a custom map provider.

Example 3: Create a custom TiledProvider and set up its commands

public class HttpsOpenStreetProvider : TiledProvider 
{ 
    /// <summary> 
    /// Initializes a new instance of the MyMapProvider class. 
    /// </summary> 
    public HttpsOpenStreetProvider() 
          : base() 
    { 
        OsmTileMapSource source = new HttpsOpenStreetMapnikSource(); 
        // required as the OSM service requires a non-stock User-Agent header 
        source.WebHeaders.Add(HttpRequestHeader.UserAgent, "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Safari/537.36 Edge/12.0"); 
        this.MapSources.Add(source.UniqueId, source); 
 
        this.SetupCommands(); 
    } 
 
    /// <summary> 
    /// Returns the SpatialReference for the map provider. 
    /// </summary> 
    public override ISpatialReference SpatialReference 
    { 
        get 
        { 
            return new MercatorProjection(); 
        } 
    } 
 
    private void SetupCommands() 
    { 
        this.CommandBindingCollection.Clear(); 
 
        string uriString = "/Telerik.Windows.Controls.DataVisualization;component/themes/road.png"; 
 
        this.RegisterSetSourceCommand( 
            typeof(HttpsOpenStreetMapnikSource), 
            LocalizationManager.GetString("MapOsmStandardCommand"), 
            null, 
            new Uri(uriString, UriKind.RelativeOrAbsolute), 
            null, 
            null); 
    } 
} 

Example 4: Create a custom OsmTileMapSource which uses an https url

public class HttpsOpenStreetMapnikSource : OsmTileMapSource 
{ 
    public HttpsOpenStreetMapnikSource() : base(@"https://{prefix}.tile.openstreetmap.org/{zoom}/{x}/{y}.png") 
    { 
    } 
} 

Example 5: Set the provider via RadMap's Provider property

this.map.Provider = new HttpsOpenStreetProvider(); 

See Also

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