ClientCallback custom control for web applications

using System;
using System.Data;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class TreeViewCallbackDisplayGrid : System.Web.UI.Page
{
    #region Page Load

    protected void Page_Load(object sender, EventArgs e)
    {
        if (IsCallback)
            return;

        if (!Page.IsPostBack)
        {
            PopulateTreeView();
            PopulateDummyGridView();
        }
    }  
    #endregion   

    #region TreeView Populate & Attach CallBack handler to it's nodes

    /// <summary>
    /// TreeView populated
    /// </summary>
    private void PopulateTreeView()
    {
        // One can load the tree here
        // Currently static nodes attached in the Designer itself.
        
        // Attach the callback handler
        AttachCallBackHandlerToNodes();
    }

    /// <summary>
    /// For attaching handler to the Nodes of the tree - Recursively
    /// </summary>
    private void AttachCallBackHandlerToNodes()
    {
        foreach (TreeNode tn in tvCallBack.Nodes)
        {
            AttachCallBack(tn);
        }
    }

    /// <summary>
    /// Handler's attached to the Nodes of the tree - Recursively
    /// </summary>
    /// <param name="tNode">tree view nodes</param>
    private void AttachCallBack(TreeNode tNode)
    {
        //Client Side callback event attached
        tNode.NavigateUrl = "javascript:OnNodeClick('" + tNode.Value + "');";
        if (tNode.ChildNodes.Count > 0)
        {
            foreach (TreeNode cNode in tNode.ChildNodes)
            {
                AttachCallBack(cNode);
            }
        }
    } 

    #endregion

    #region CallBack Event Handler
    // Bubbled event for Callback control placed
    // One can handle the operations required during the callback out here.
    protected void CallBackControl_Perform(object sender, EventArgs e)
    {
        string argParameter = ((MyCustomControls.MyCustomCallBackControl)sender).ArgumentParameter;
        DataTable dt = RetrieveDataTable(argParameter);
        gvTest.DataSource = dt;
        gvTest.DataBind();

        //Setting of the response output for callback
        using (System.IO.StringWriter sw = new System.IO.StringWriter())
        {
            gvTest.RenderControl(new HtmlTextWriter(sw));
            ((MyCustomControls.MyCustomCallBackControl)sender).RenderedOutput = sw.ToString();
        }
    } 
    #endregion

    #region GridView Operations & GridView Data Retrieval

    /// <summary>
    /// Dummy Grid View populated. One can populate the Root node related Data. 
    /// </summary>
    protected void PopulateDummyGridView()
    {
        DataTable dt = new DataTable("Table1");

        DataColumn dc1 = new DataColumn("ID");
        dt.Columns.Add(dc1);

        dt.Rows.Add("1");
        dt.Rows.Add("2");

        gvTest.DataSource = dt;
        gvTest.DataBind();
    }

    /// <summary>
    /// Retrieval of Test Data
    /// </summary>
    /// <param name="param">Parameter in order to retrieve the data</param>
    /// <returns></returns>
    private DataTable RetrieveDataTable(string param)
    {
        DataTable dt = new DataTable("Table1");

        DataColumn dc1 = new DataColumn("ID");
        DataColumn dc2 = new DataColumn("Caption");
        DataColumn dc3 = new DataColumn("Description");
        DataColumn dc4 = new DataColumn("Value");
        dt.Columns.Add(dc1);
        dt.Columns.Add(dc2);
        dt.Columns.Add(dc3);
        dt.Columns.Add(dc4);

        dt.Rows.Add(param, "Name" + param, "Who is responsible" + param, "NodeValue" + param);
        dt.Rows.Add(param, "Education" + param, "Detail about educational background" + param, "NodeValue" + param);
        dt.Rows.Add(param, "Experience" + param, "How much of professional experience" + param, "NodeValue" + param);
        dt.Rows.Add(param, "Address" + param, "Where do you stay?" + param, "NodeValue" + param);

        return dt;
    } 
    #endregion
}