Index was out of range. Must be non-negative and less than the size of the collection.Parameter name: index

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C#

ASP.NET

C#4.0

hi can any one help me to solve this? am binding data to dropdownlist.


html code

<telerik:RadComboBox ID="cmbEPS" runat="server" Height="22px" Width="200px">
                                    <ItemTemplate>
                                        <div onclick="StopPropagation(event)">
                                            <asp:TreeView ID="tvWBS" runat="server" NodeStyle-NodeSpacing="2px"
                                                ShowLines="true">
                                                <HoverNodeStyle CssClass="CustomNodeColor" />
                                                <SelectedNodeStyle BackColor="#5B5B5B" ForeColor="White" HorizontalPadding="3px" />
                                                <NodeStyle ForeColor="#000000" />
                                            </asp:TreeView>
                                        </div>
                                    </ItemTemplate>
                                </telerik:RadComboBox>
                                <asp:RequiredFieldValidator ID="rfvActivityGroup" runat="server" ControlToValidate="cmbActivityGroup"
                                    Display="None" ErrorMessage="Select EPS" SetFocusOnError="True" ValidationGroup="g"
                                    Visible="true"></asp:RequiredFieldValidator>

.......................................................................................................................................................................................................
in .cs

RadComboBox cmbEPS = (RadComboBox)phDynamic.FindControl("cmbEPS");
       if (cmbEPS !=null)
       {

               RadTreeView rtvEPS = (RadTreeView)cmbEPS.Items[0].FindControl("rtvEPS");//in this line am getting error..

thank you