Related ComboBoxes, set after postback clientside

[Laz]

In my szenario i have a table. Inside this table there is an RadToolBar with two RadComboBoxes.

My problem is the handling of the Related ComboBoxes, after a postback. After the postback the second RadComboBox lost there

Datasource. What I try to do is to set second RadComboBox clientside in the pageLoad Function.

Depending of the value in the first RadComboBox (that i got in the pageLoad function) i try to refresh the datasource for the second RadComboBox.

Here is my code snippet:

    <script type="text/javascript">
        //global variables for the countries and cities comboboxes
        var RadGrid1;
        var WTypesCombo;
        var CDecisonCombo;

        //------------------------------------------------------------------------
        function GetGridObject(sender, eventArgs) {
            RadGrid1 = sender;
        }

        //------------------------------------------------------------------------
        function pageLoad() {
            // initialize the global variables
            // in this event all client objects
            // are already created and initialized
            WTypesCombo                 = $find('<%=rdtbWl.FindItemByText("rtbWTypes").FindControl("rcbWTypes").ClientID %>');
            CDecisonCombo               = $find('<%=rdtbWl.FindItemByText("rtbCDecision").FindControl("rcbCDecision").ClientID %>');

            //Get the selected type
            //this will only triggert if a submit event exists
            var SelectedIndex = document.getElementById("<%= SelectedWType.ClientID %>").value;

            if (SelectedIndex != "0") {
                //HERE REFRESH THE SECOND RADCOMBOBOX
                CDecisonCombo.requestItems(SelectedIndex.get_text(), false);
            }

        }
        //------------------------------------------------------------------------
        function OnClientSelectedIndexChanged(sender, eventArgs) {

            var item = eventArgs.get_item();
            //the first item is always the item to show all rows
            //we can not use a value because all values are identical. Only text are unique
            if (item.get_index() == "0") {
                //Set worklist type in hidden field to store in session, when the submit event is fired
                document.getElementById("<%= SelectedWType.ClientID %>").value = item.get_index();
            }
            else {
                //Set worklist type in hidden field to store in session, when the submit event is fired
                document.getElementById("<%= SelectedWType.ClientID %>").value = item.get_text();
            }

            CDecisonCombo.set_text("Loading...");

            // if a Worklisttyp is selected
            if (item.get_index() > 0) {
                // this will fire the ItemsRequested event of the
                // combobox passing the WtypID as a parameter
                CDecisonCombo.requestItems(item.get_text(), false);
            }
            else {
                // the -Select a continent- item was chosen
                CDecisonCombo.set_text(" ");
                CDecisonCombo.clearItems();
            }
        }

        //------------------------------------------------------------------------
        function ItemsLoaded(combo, eventArqs) {

            if (combo.get_items().get_count() > 0) {
                // pre-select the first item
                combo.set_text(combo.get_items().getItem(0).get_text());
                combo.get_items().getItem(0).highlight();
            }
        }
        //------------------------------------------------------------------------

    </script>

</telerik:RadCodeBlock>

<table cellpadding="0" cellspacing="0" border="0" width="100%">
    <tr>
        <td>
            <telerik:RadToolBar ID="rdtbWl" runat="server"
                Style="display: block; float: none" Visible="true"
                Width="100%" OnClientButtonClicked="OnClientButtonClicking"
                OnButtonClick="rdtbWl_ButtonClick"
                OnClientMouseOver="clientMouseOver"
                OnClientMouseOut="clientMouseOut"
                meta:resourcekey="rdtbWlResource1">
                <CollapseAnimation Type="OutQuint" Duration="200"></CollapseAnimation>
                <Items>
                    <telerik:RadToolBarButton Value="rtbWTypes" Text="rtbWTypes">
                        <ItemTemplate>
                            <telerik:RadComboBox ID="rcbWTypes"
                                                    runat="server"
                                                    CssClass="DefaultText"
                                                    OnClientSelectedIndexChanged="OnClientSelectedIndexChanged"
                                                    DataTextField="Shorttext"
                                                    DataValueField="Shorttext"
                                                    HighlightTemplatedItems="True">
                                <CollapseAnimation Duration="200" Type="OutQuint" />
                            </telerik:RadComboBox>
                        </ItemTemplate>
                    </telerik:RadToolBarButton>
                    <telerik:RadToolBarButton Value="rtbCDecision" Text="rtbCDecision">
                        <ItemTemplate>
                            <telerik:RadComboBox ID="rcbCDecision"
                                                    runat="server"
                                                    CssClass="DefaultText"
                                                    OnClientItemsRequested="ItemsLoaded"
                                                    OnItemsRequested="rcbCDecision_ItemsRequested">
                                <CollapseAnimation Duration="200" Type="OutQuint" />
                            </telerik:RadComboBox>
                        </ItemTemplate>
                    </telerik:RadToolBarButton>
                    <telerik:RadToolBarButton Text="rtbColumnSetDecision"
                        Value="rtbColumnSetDecision"
                        runat="server" PostBack="false"
                        meta:resourcekey="RadToolBarButtonResource4" >
                    </telerik:RadToolBarButton>
                    <telerik:RadToolBarButton Text="rtbCDecisionExecute"
                        Value="rtbCDecisionExecute"
                        runat="server" PostBack="true">
                    </telerik:RadToolBarButton>
                </Items>
            </telerik:RadToolBar>
        </td>
    </tr>
</table>

<%--store the selected Type--%>
 <asp:HiddenField ID="SelectedWType" runat="server" Value="0"/>

The same example we find in the telerik demos: [Related ComboBoxes]
http://demos.telerik.com/aspnet-ajax/combobox/examples/functionality/multiplecomboboxes/defaultcs.aspx

Thanks for any help

[Yana]

Hello Laz,

Please set EnableLoadOnDemand property of rcbCDecision combobox to "true" in order to preserve the loaded items.

Regards,
Yana
the Telerik team

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[Laz]

Thanks for the great support.

Always timely and competent!

[tomekm]

Does this solution preserve SelectedValue property?

I have three related Comboboxes and I am using your technique

Unfortunately, there are also other fields on form that causes validation, and if it fails, text remains in comoboxes thank to EnableLoadOnDemand, however on serverside - SelectedValue is equal to null.

[Laz]

Hi,
in my code szenario the selected values preserve. But i didn´t have any validation!

Do you have set EnableLoadOnDemand property of your control x to "true" in order to preserve the loaded items?

[tomekm]

Yes! Without EnabloLoadOnDemand text dissapeared as well. With EnabloLoadOnDemand = true it preserves but SelectedValue does not.

[Echarbeneau]

I am also using this and when the page posts back I lose all of the items for the linked combo boxes. Is this normal?

Regards,
Ed C.

[Echarbeneau]

Alright, I figured this out on my own. Thank you for posting, the information I found here led me to my answer.

Here is my final working solution:

<telerik:RadComboBox ID="rcbCompany" runat="server" Width="200px" CssClass="field"
            CausesValidation="False" OnClientSelectedIndexChanging="LoadLocations"
            EnableLoadOnDemand="True">
            <CollapseAnimation Type="OutQuint" Duration="200"></CollapseAnimation>
        </telerik:RadComboBox>
<telerik:RadComboBox CssClass="field" ID="rcbCompanyLocation" runat="server" Width="200px"
            OnClientItemsRequested="ItemsLoaded"
            OnItemsRequested="rcbCompanyLocation_ItemsRequested" EnableLoadOnDemand="True">
            <CollapseAnimation Type="OutQuint" Duration="200"></CollapseAnimation>
        </telerik:RadComboBox>

// there are two combos linked
// rcbCompany(master)
// rcbCompanyLocation

 var radcomboLocations;

    function pageLoad() {
        // initialize the global variables
        // in this event all client objects
        // are already created and initialized
        radcomboLocations = $find("<%= rcbCompanyLocation.ClientID %>");

    }

    function LoadLocations(combo, eventArqs) {
        var item = eventArqs.get_item();
        radcomboLocations.set_text("Loading...");
        radcomboLocations.requestItems(item.get_value(), false)
        }
    }

    function ItemsLoaded(combo, eventArqs) {

        if (combo.get_items().get_count() > 0) {
            // pre-select the first item
            combo.set_text(combo.get_items().getItem(0).get_text());
            combo.get_items().getItem(0).highlight();
            combo.showDropDown();
        }

    }

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not Page.IsPostBack Then
            'Do page load stuff
            BindCompany()
        Else
            'Rebind slaved combo box items
            'rcbCompanyLocation.SelectedValue is retained by setting the property
            '    EnableLoadOnDemand = True
            BindLocation(rcbCompany.SelectedValue)
        End If
     Protected Sub rcbCompanyLocation_ItemsRequested(ByVal o As Object, ByVal e As Telerik.Web.UI.RadComboBoxItemsRequestedEventArgs) Handles rcbCompanyLocation.ItemsRequested
        BindLocation(e.Text)
    End Sub