ASP.NET

protected void Page_Load(object sender, EventArgs e)
{        
    BindControls();
}

#region Data Binding Procedures

private void BindControls()
{
    this.BindDistributor();
    this.BindModuleName();
    this.DataBind();
}

private void BindDistributor()
{
    this.BindDistributorID();
    this.BindDistributorName();
}

private void BindDistributorID()
{
    SqlConnection SqlConn = DataAccess.OpenConnection();
    DataSet dsDistributor;

    if (chkShowAllDistributors.Checked)
    {
        SqlParameter SqlParam = new SqlParameter("ShowAll", 'Y');
        dsDistributor = DataAccess.GetDataSet(SqlConn, CommandType.StoredProcedure,
            SPs.GetDistributorName, new SqlParameter[] { SqlParam });
    }
    else
    {
        dsDistributor = DataAccess.GetDataSet(SqlConn, CommandType.StoredProcedure, "GetDistributorName");
    }

    if (dsDistributor.Tables.Count > 0)
    {
        this.ddlDistributor.DataSource = dsDistributor.Tables[0];
        this.ddlDistributor.DataValueField = Colums.DistributorID;
        this.ddlDistributor.DataTextField = Colums.DistributorShortName;
    }
}

private void BindDistributorName()
{
    DataView dvDistributor = ((DataTable)ddlDistributor.DataSource).Copy().DefaultView;
    if (this.ddlDistributor.SelectedIndex != -1)
    {
        dvDistributor.RowFilter = Colums.DistributorID + "='" + ddlDistributor.SelectedValue.ToString() + "'";
        if (dvDistributor.Count > 0)
        {
            this.lblDistributorName.Text = dvDistributor[0][Colums.DistributorID]
                + " - " + dvDistributor[0][Colums.DistributorName];
        }
    }
}

#endregion

protected void chkShowAllDistributors_CheckedChanged(object sender, EventArgs e)
{
    this.BindDistributor();
}

<frameset cols="25%,*">
    <frame name="TreeView" src="TreeViewMenu.aspx" />
    <frameset rows="40%,*">
        <frame name="Parameters" src="UploadPage.aspx" />
        <frame name="DataDisplay" src="DataDisplay.aspx" />
    </frameset>
</frameset>

protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
{
    string strSelected = ((TreeView)sender).SelectedNode.Value.ToString();
    
    switch (strSelected)
    {
        case "Node1":
            // Response.Write(strSelected);
            // What code should I put here...
            break;
    }
}

<asp:CheckBox ID="chkShowAllDistributors" runat="server" checked="false" Text="Show All Distributors"  OnCheckedChanged="chkShowAllDistributors_CheckedChanged"/><br /><br />
  <asp:DropDownList ID="ddlDistributor" runat="server" OnSelectedIndexChanged="ddlDistributor_SelectedIndexChanged"></asp:DropDownList>

protected void chkShowAllDistributors_CheckedChanged(object sender, EventArgs e)
 {
     this.BindDistributor();
 }
 protected void ddlDistributor_SelectedIndexChanged(object sender, EventArgs e)
 {
     this.BindDistributor();
 }