3 Drop downs depending each other

[Nani]

Here the online solutions depending drop down not vice versa. I have there drop down , data populate using wcf service. Please consider my scenario 
Step 1 : i am requesting first drop downs  values ( OnClientItemsRequesting="OnClientItemsRequesting" ) i am getting 500 records.
    function OnClientItemsRequesting(sender, e) {
        var context = e.get_context();
        context["UpdateKeys"] = UpdateKeys();// thjis function give 3 dropdown selected value
    }

Step 2: I am requesting second drop downs values now i am getting 400 records ( these 400 records are depending values on first drop down )
Step 3: I am requesting third drop downs values now i am getting 300 records ( these 400 records are depending values on first & second drop downs )
Step 4: Now i am again requesting First drop down values . This time i need to get only 50(which are depending on 2&3 drop downs). i am update getting 50 records when i am start type on drop down text box.
                            But i need to update when i open drop down. Here have client event OnClientDropDownOpening or OnClientDropDownOpened. But this event doesn't have e.get_context(); and all auto wcf calling like OnClientItemsRequesting event.

<telerik:RadComboBox runat="server" ID="dropdown1" CloseDropDownOnBlur="true" EnableAjaxSkinRendering="true"
        EnableTextSelection="true" ShowWhileLoading="true" EnableLoadOnDemand="true"
       OnClientItemsRequesting="OnClientItemsRequesting"
        ShowMoreResultsBox="true" MinFilterLength="3" EnableVirtualScrolling="true" EmptyMessage="Type refresh values..."
        Width="380" Height="250">
        <WebServiceSettings Path="/Services/service.svc" Method="FillFristDrop" />
    </telerik:RadComboBox>
     <telerik:RadComboBox runat="server" ID="dropdown2" CloseDropDownOnBlur="true" EnableAjaxSkinRendering="true"
        EnableTextSelection="true" ShowWhileLoading="true" EnableLoadOnDemand="true"
       OnClientItemsRequesting="OnClientItemsRequesting"
        ShowMoreResultsBox="true" MinFilterLength="3" EnableVirtualScrolling="true" EmptyMessage="Type refresh values..."
        Width="380" Height="250">
        <WebServiceSettings Path="/Services/service.svc" Method="FillSecondDrop" />
    </telerik:RadComboBox>
     <telerik:RadComboBox runat="server" ID="dropdown3" CloseDropDownOnBlur="true" EnableAjaxSkinRendering="true"
        EnableTextSelection="true" ShowWhileLoading="true" EnableLoadOnDemand="true"
       OnClientItemsRequesting="OnClientItemsRequesting"
        ShowMoreResultsBox="true" MinFilterLength="3" EnableVirtualScrolling="true" EmptyMessage="Type refresh values..."
        Width="380" Height="250">
        <WebServiceSettings Path="/Services/service.svc" Method="FillThirdDrop" />
    </telerik:RadComboBox>


<script language="javascript" type="text/javascript">
    function OnClientItemsRequesting(sender, e) {
        var context = e.get_context();
        context["UpdateKeys"] = UpdateKeys();
    }
    function UpdateKeys() {
       return values // return remaing 2 dropdown selected value
    }
</script>

[Hristo Valyavicharski]

Hi,

Try to call first combo's requestItems() method. This will automatically fire OnClientItemsRequesting and you will be able to get e.get_context(); in the same way as you did:

function OnClientDropDownOpening(sender, args) {
    var firstCombo = $('dropdown1');
    firstCombo.requestItems();
}

Regards,
Hristo Valyavicharski
the Telerik team