Display custom shape layers using GeoJSON

Environment

Product

RadMap for ASP.NET AJAX

Description

In this article you will see how to display custom shape layers using GeoJSON in RadMap.

Solution

• Add a HiddenField which will be used for storing the GeoJSON coordinates. Additioanlly, attach the OnInitialize client-side event to the Map and employ an event handler to it.

ASPX

<asp:HiddenField runat="server" ID="HiddenGeoJSON" />

<telerik:RadMap runat="server" ID="RadMap1" Zoom="2" Width="1000" Height="500">
    <ClientEvents OnInitialize="OnInitialize" />
    <CenterSettings Latitude="30" Longitude="10" />
    <LayerDefaultsSettings>
        <ShapeSettings>
            <StyleSettings>
                <FillSettings Color="green" />
                <StrokeSettings Color="black" Width="2" />
            </StyleSettings>
        </ShapeSettings>
    </LayerDefaultsSettings>
    <LayersCollection>
        <telerik:MapLayer Type="Shape" ZIndex="999999">
        </telerik:MapLayer>
        <telerik:MapLayer Type="bing"
            UrlTemplate="http://a.tile.opencyclemap.org/transport/#= zoom #/#= x #/#= y #.png">
        </telerik:MapLayer>
    </LayersCollection>
</telerik:RadMap>

• In the event handler, set the data source of the layer to the value of the hidden field.

JS

function OnInitialize(sender, args) {
    var originalOptions = args.get_options();
    var geoJSON = document.getElementById("<%=HiddenGeoJSON.ClientID%>").value;

    originalOptions.layers[0].dataSource = { 
        data: JSON.parse(geoJSON) 
    };

    args.set_options(originalOptions);
}

• In the code-behind, add the lattitude/longtitude coordinates for the points.

C#

protected void Page_Load(object sender, EventArgs e)
{
    HiddenGeoJSON.Value = "[{\"type\": \"Polygon\",\"coordinates\": [[[20, 10], [40, 40], [10, 40], [10, 20], [20, 10]]]}]";
}

VB

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If Not IsPostBack Then
        HiddenGeoJSON.Value = "[{""type"": ""Polygon"",""coordinates"": [[[30, 10], [40, 40], [20, 40], [10, 20], [30, 10]]]}]"
    End If
End Sub