Load on demand using ajax combo

[Rachana]

I need to use Cascading combo boxes for that to avoid post backs i selected Load on demand Ajax Combo....
for first time selected values its working fine..when i will change item in the first combo-box the second combo box items are not get updated.my code is below

<telerik:RadComboBox ID="RadComboState" runat="server" Width="250px" Height="150px"
                                                EmptyMessage="Select a state" EnableLoadOnDemand="True" ShowMoreResultsBox="true"
                                                EnableVirtualScrolling="true" OnItemsRequested="RadComboState_ItemsRequested">
                                            </telerik:RadComboBox>
  <telerik:RadComboBox ID="RadComboInstitution" runat="server" Width="250px" Height="150px"
                                                EmptyMessage="Select an institution" EnableLoadOnDemand="True" ShowMoreResultsBox="true"
                                                EnableVirtualScrolling="true" OnItemsRequested="RadComboInstitution_ItemsRequested"
                                                OnClientItemsRequesting="GetSelectedState">
                                            </telerik:RadComboBox>

function GetSelectedState(sender, eventArgs) {

            var SelectedState;

            var combo = Telerik.Web.UI.RadComboBox.ComboBoxes[0];

            SelectedState = combo.get_value();

            var context = eventArgs.get_context();

            context["StateId"] = SelectedState;

             

        }      

protected void RadComboState_ItemsRequested(object o, RadComboBoxItemsRequestedEventArgs e)

    {

        RadComboState.Items.Clear();

        DataSet data = PoulateStates();

        if (data.Tables.Count > 0 && data.Tables[0].Rows[0][0].ToString() == "0")

        {

            int itemOffset = e.NumberOfItems;

            int endOffset = Math.Min(itemOffset + ItemsPerRequest, data.Tables[0].Rows.Count);

            e.EndOfItems = endOffset == data.Tables[0].Rows.Count;

            for (int i = itemOffset; i < endOffset; i++)

            {

                RadComboState.Items.Add(new RadComboBoxItem(data.Tables[0].Rows[i]["State_Name"].ToString(),

                                                            data.Tables[0].Rows[i]["intPkVal"].ToString()));

            }

            e.Message = GetStatusMessage(endOffset, data.Tables[0].Rows.Count);

        }

        else

        {

            RadComboBoxItem item = new RadComboBoxItem();

            item.Value = "-1";

            if (Session["COUNTRY"] != null && Session["COUNTRY"].ToString().ToUpper() == "MARSHALL ISLANDS")

                item.Text = "No Island Exists";

            else

                item.Text = "No State Exists";

            RadComboState.Items.Add(item);

        }

    }

     

    protected void RadComboInstitution_ItemsRequested(object o, RadComboBoxItemsRequestedEventArgs e)

    {

        RadComboInstitution.Items.Clear();

        DataSet Institution = new DataSet();

        

        try

        {

            string StateId = e.Context["StateId"].ToString();

            Institution = populateInstitution(StateId);

 

            if (Institution.Tables[0].Rows[0][0].ToString() == "0")

            {

                int itemOffset = e.NumberOfItems;

                int endOffset = Math.Min(itemOffset + ItemsPerRequest, Institution.Tables[0].Rows.Count);

                e.EndOfItems = endOffset == Institution.Tables[0].Rows.Count;

 

                for (int i = itemOffset; i < endOffset; i++)

                {

                    RadComboInstitution.Items.Add(

                        new RadComboBoxItem(Institution.Tables[0].Rows[i]["Institution_Name"].ToString(),

                                            Institution.Tables[0].Rows[i]["InstitutionId"].ToString()));

                }

 

                e.Message = GetStatusMessage(endOffset, Institution.Tables[0].Rows.Count);             

            }

            else

            {

                RadComboBoxItem item = new RadComboBoxItem();

                item.Value = "-1";

                item.Text = "No Institution Exists";

                RadComboInstitution.Items.Add(item);

            }

 

        }

        catch (Exception ex)

        {

        }

    }

[Princy]

Hi Rachana,

Here is the code that I tried based on your scenario which works as expected. Refer  this demo for more.

ASPX:

<telerik:RadComboBox ID="RadComboBox1" runat="server" OnItemsRequested="RadComboBox1_ItemsRequested" OnClientSelectedIndexChanging="loadProducts">
</telerik:RadComboBox>
<telerik:RadComboBox ID="RadComboBox2" runat="server" OnItemsRequested="RadComboBox2_ItemsRequested" OnClientItemsRequested="ItemsLoaded">
</telerik:RadComboBox>

JS:

<script type="text/javascript">
 var productCombo;
 function pageLoad()
 {
  productCombo = $find("<%= RadComboBox2.ClientID %>");
 }
 function loadProducts(sender, eventArgs)
 {
  var item = eventArgs.get_item();
  productCombo.set_text("Loading...");
  if (item.get_index() > 0)
  {
   productCombo.requestItems(item.get_value(), false);
  }
  else
  {
   productCombo.set_text("");
   productCombo.clearItems();
  }
 }
 function ItemsLoaded(sender, eventArgs)
 {
   if (sender.get_items().get_count() > 0)
   {
    sender.set_text(sender.get_items().getItem(0).get_text());
    sender.get_items().getItem(0).highlight();
   }
   sender.showDropDown();
 }
</script>

C#:

protected void Page_Load(object sender, EventArgs e)
{
 if (!Page.IsPostBack)
 {
  loadCategories();
 }
 else if (!Page.IsCallback)
 {
  loadProducts(RadComboBox1.SelectedValue);
 }
}

protected void loadCategories()
 {
  SqlDataAdapter adapter = new SqlDataAdapter();
  adapter.SelectCommand = new SqlCommand("SELECT * FROM Customers ORDER By CompanyName", conn);
  DataTable dt = new DataTable();
  adapter.Fill(dt);
  RadComboBox1.DataTextField = "CustomerID";
  RadComboBox1.DataValueField = "CustomerID";
  RadComboBox1.DataSource = dt;
  RadComboBox1.DataBind();
  RadComboBox1.Items.Insert(0, new RadComboBoxItem("- Select.... -"));
}

protected void loadProducts(string CategoryID)
 {
  SqlDataAdapter adapter = new SqlDataAdapter();
 adapter.SelectCommand = new SqlCommand("SELECT * FROM Orders WHERE CustomerID=@CustomerID ORDER By CustomerID", conn);
 adapter.SelectCommand.Parameters.AddWithValue("@CustomerID", CategoryID);
 DataTable dt = new DataTable();
 adapter.Fill(dt);
 RadComboBox2.DataTextField = "OrderID";
 RadComboBox2.DataValueField = "OrderID";
 RadComboBox2.DataSource = dt;
 RadComboBox2.DataBind();
}

protected void RadComboBox1_ItemsRequested(object sender, Telerik.Web.UI.RadComboBoxItemsRequestedEventArgs e)
 {
  loadCategories();
 }
protected void RadComboBox2_ItemsRequested(object sender, Telerik.Web.UI.RadComboBoxItemsRequestedEventArgs e)
 {
  loadProducts(e.Text);
 }

Thanks,
Princy.