Unable to find radlistbox on ASP.NET client side button click event

See more:

VB

ASP.NET

Telerik

Hi I have a radlistbox with SelectionMode="Multiselect". I want to get the count of checked items of listbox on button click. I tried to get the count by finding control on button click event but i am not able to find the control.


But I am not able to find control. Can anyone suggest a better way to do this. My main objective is to get count of checked items of list box on button click

What I have tried:

HTML Code:

<telerik:radajaxpanel id="RadAjaxPanel1" runat="server" width="100%">

<div>

<asp:table>

<asp:tablerow>
                <asp:tableheadercell>
                <telerik:radlabel id="RadLabel_abc" runat="server" text="ABC">
                
<asp:tablerow>

<asp:tablecell>

<telerik:radlistbox id="rlbAbc" runat="server" 
="" height="100px" width="480px" allowtransfer="false" allowtransferondoubleclick="false" transfertoid="rlbChosen" enabledraganddrop="true" onclienttransferring="rlbAbc_OnClientTransferring" checkboxes="true" buttonsettings-showtransferall="false" enableviewstate="false" selectionmode="Multiple">

</div>

.VB File

Protected Sub RadButton_AddToList_Click(sender As Object, e As EventArgs)

GetSelectedItemText("rlbABC")

End Sub

Public Function GetSelectedItemText(ByVal controlID As String) As String
        Dim theListbox As RadListBox = CType(FindControl(controlID), RadListBox)
        For idx As Integer = 0 To theListbox.Items.Count - 1
            Dim li As RadListBoxItem = theListbox.Items(idx)

            If theListbox.Items(idx).Selected = True Then
                Return theListbox.Items(idx).Text
            End If
        Next

        Return Nothing
    End Function