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Web Service Binding

Instead of supplying a NodeExpand event handler to add nodes on-demand to the TreeView, you can let the TreeView call on a WebService to service the request. The path to the web service and the name of the service method are specified in the WebServiceSettings Path and Method properties:

<telerik:radtreeview id="RadTreeView1" runat="server" onclientnodepopulating="nodePopulating">
    <Nodes>
        <telerik:RadTreeNode runat="server" Text="Root RadTreeNode1" ExpandMode="WebService"
            Value="1">
        </telerik:RadTreeNode>
        <telerik:RadTreeNode runat="server" Text="Root RadTreeNode2" ExpandMode="WebService"
            Value="2">
        </telerik:RadTreeNode>
    </Nodes>
    <WebServiceSettings Path="ProductCategories.asmx" Method="GetTreeViewCategories" />
</telerik:radtreeview>
function nodePopulating(sender, eventArgs) {

    var node = eventArgs.get_node();
    var context = eventArgs.get_context();
    context["CategoryID"] = node.get_value();
}

The HTTP method by default is POST. To change that you can set the UseHttpGet property of the WebServiceSettings to True. This property is added in Q1 2009 release.

To use the integrated support, the Web service should have the signature as shown in the code example below.

note

Notice in the code below:

  • The ScriptService attribute marks the ProductCategories class and makes the web method callable from client-side script and therefore available to AJAX.

  • The signature of the web method includes parameters for a RadTreeNodeData and an object. The RadTreeNodeData parameter represents the parent node being >populated. The second parameter is an object that contains context information. Cast the object as IDictionary as shown in the example below. You can then >retrieve values that have been placed in the dictionary earlier in the OnClientNodePopulating client event.

  • The array of RadTreeNodeData returned by the method is used to store the data that will populate the child nodes. Create and assign properties to the >RadTreeNodeData array members just as you would to the actual child nodes.>

// supports IDictionary
using System.Collections.Generic;
// supports ScriptService attribute
using System.Web.Script.Services;
// supports WebMethod attribute
using System.Web.Services;
using Telerik.Web.UI;
[ScriptService]
public class ProductCategories : WebService
{
   [WebMethod]
   public RadTreeNodeData[] GetTreeViewCategories(RadTreeNodeData node, object context)
   {
       // extract the "context" dictionary information. OnClientNodePopulating event loads the dictionary
       IDictionary<string, object> contextDictionary = (IDictionary<string, object>)context;
// create the array of RadTreeNodeData that will be returned by this method
       List<RadTreeNodeData> result = new List<RadTreeNodeData>();
// add data for child nodes
       RadTreeNodeData nodeData = new RadTreeNodeData();
       nodeData.Text = "child" + contextDictionary["CategoryID"] + i;
       nodeData.Value = contextDictionary["CategoryID"].ToString() + i;
       result.Add(nodeData);
       return result.ToArray();
   }
} 
' supports IDictionary
Imports System.Collections.Generic
' supports ScriptService attribute
Imports System.Web.Script.Services
' supports WebMethod attribute
Imports System.Web.Services
Imports Telerik.Web.UI
<ScriptService()> _
Public Class ProductCategories
    Inherits WebService
    <WebMethod()> _
    Public Function GetTreeViewCategories(ByVal node As RadTreeNodeData, ByVal context As Object) As RadTreeNodeData()
        ' extract the "context" dictionary information. OnClientNodePopulating event loads the dictionary
        Dim contextDictionary As IDictionary(Of String, Object) = DirectCast(context, IDictionary(Of String, Object))
        ' create the array of RadTreeNodeData that will be returned by this method
        Dim result As New List(Of RadTreeNodeData)()
        ' add data for child nodes
        Dim nodeData As New RadTreeNodeData()
        nodeData.Text = "child" + contextDictionary("CategoryID") + i
        nodeData.Value = contextDictionary("CategoryID").ToString() + i
        result.Add(nodeData)
        Return result.ToArray()
    End Function
End Class

For a live example of using a Web service to populate a RadTreeView, see Populate From Web Service.