Load items asynchronously

[Quantesys IT]

Hello,

I have a UserControl with different fields and a RadComboBox. I want to reduze the time that the user needs to wait (actually the RadComboBox is populated on server-side and it takes a lot of time).

The content of the RadComboBox is not required immediatly; the user needs to fill some fields before. I want to use a WebService or HttpHandler to fill the RadComboBox asynchronously and make it completly "invisible" for the user.

I found some solutions to load the items using a WebService/WCF but the request is sent only when the user try to display the RadComboBox's content (LoadOnDemand)!

Is there a solution to call the WebService automatically after the page load without an interaction of the user?

Thank you for your help.

[Kalina]

Hi Quantesys IT,

Let me suggest you call the web service and perform a request for items at OnClientLoad event of the RadComboBox:

function OnClientLoad(sender)
{
    sender.requestItems("", false);
}

All the best,
Kalina
the Telerik team

[Quantesys IT]

Thank you for your help, it works perfectly!

But now I have another problem :-(

My ComboBox needs to fire a PostBack on index changed and I need to get some attributes from server-side. Before the use of WebService it was easy to do the job because of SelectedItem object.

Here is a part of my WebService:

RadComboBoxData result = new RadComboBoxData();
List<RadComboBoxItemData> items = new List<RadComboBoxItemData>();

...

RadComboBoxItemData item = new RadComboBoxItemData();
item.Text = myObject.Name;
item.Value = myObject.Id.ToString();
item.Attributes.Add("FirstAttribute", myObject.FirstAttribute);
item.Attributes.Add("SecondAttribute", myObject.SecondAttribute);
items.Add(item);

result.Items = items.ToArray();

return result;

How can I get the value of these additional attributes when the OnSelectedIndexChanged event is fired?

Thank you for your help

[Kalina]

Hello,

RadComboBox items loaded via Load On Demand are not accessible at server-side - please find more details about this issue at this help article.
Let me suggest you add a HiddenField at your page and store the value, text and/or attribute of the selected RadComboBoxItem in it handling the OnClientSelectedIndexChanged event in this manner:

<script type="text/javascript">

    var hiddenField;

     

    function pageLoad() {                

        hiddenField = document.getElementById("<%=selectedValues.ClientID %>"

    }

    

    function OnClientSelectedIndexChangedHandler(sender, eventArgs) {

     

        hiddenField.value = sender.get_selectedItem().get_value();

       


    }

 

</script>

<asp:HiddenField ID="selectedValues" runat="server" EnableViewState="true" />


 

<telerik:RadComboBox ID="RadComboBox1" runat="server"

    OnClientSelectedIndexChanged="OnClientSelectedIndexChangedHandler"  ... >

Then you can easily obtain the value of the HiddenField at server-side:

string parameters = selectedValues.Value;

All the best,
Kalina
the Telerik team

[Quantesys IT]

Thank your for your help, it works great!