Cascading DropDownLists Inside Telerik RadGrid

protected void RadComboBox1_SelectedIndexChanged(object sender, Telerik.Web.UI.RadComboBoxSelectedIndexChangedEventArgs e)
        {
            // Get the Country DropDownList first.
            RadComboBox ddlBranch = (RadComboBox)sender;

            // Get the current GridView Row, from which the DropDownList is selected.
            GridEditableItem currentRow = (GridEditableItem)ddlBranch.NamingContainer;

            // Now let's find the City DropDownList on the same GridView Row.
            DropDownList ddlCity = (DropDownList)currentRow.FindControl("ddlAgent");

            if (ddlBranch != null && ddlBranch.SelectedIndex > 0 && ddlCity != null)
            {
                relife_part2Entities db = new relife_part2Entities();
                int? companyidfk=Convert.ToInt32(ddlBranch.SelectedValue);
                ddlCity.DataSource = db.tbl_policymaster.Where(x => x.companyidfk == companyidfk).ToList();
                ddlCity.DataTextField = "fullname";
                ddlCity.DataValueField = "policyID";
              
                ddlCity.DataBind();
                ddlCity.Items.Insert(0, "Select");
            }
            else if (ddlCity != null)
            {
                ddlCity.Items.Clear();
            }
        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            // Get the Country DropDownList first.
            DropDownList ddlBranch = (DropDownList)sender;

            // Get the current GridView Row, from which the DropDownList is selected.
            GridEditableItem currentRow = (GridEditableItem)ddlBranch.NamingContainer;

            // Now let's find the City DropDownList on the same GridView Row.
            DropDownList ddlCity = (DropDownList)currentRow.FindControl("ddlAgent");

            if (ddlBranch != null && ddlBranch.SelectedIndex > 0 && ddlCity != null)
            {
                relife_part2Entities db = new relife_part2Entities();
                int? companyidfk = Convert.ToInt32(ddlBranch.SelectedValue);
                ddlCity.DataSource = db.tbl_policymaster.Where(x => x.companyidfk == companyidfk).ToList();
                ddlCity.DataTextField = "fullname";
                ddlCity.DataValueField = "policyID";

                ddlCity.DataBind();
                ddlCity.Items.Insert(0, "Select");
            }
            else if (ddlCity != null)
            {
                ddlCity.Items.Clear();
            }
        }


Html Code

  <div>
            <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server"></telerik:RadAjaxManager>
            <telerik:RadScriptManager ID="RadScriptManager1" runat="server"></telerik:RadScriptManager>
            <telerik:RadGrid ID="RadGrid1" runat="server" AllowFilteringByColumn="True" AllowSorting="True" DataSourceID="SqlDataSource1" GroupPanelPosition="Top" AllowPaging="True" OnItemCommand="RadGrid1_ItemCommand">
                <MasterTableView AutoGenerateColumns="False" DataSourceID="SqlDataSource1" EditMode="PopUp">
                   
                    <Columns>
                        <telerik:GridEditCommandColumn UniqueName="EditCommandColumn">
                        </telerik:GridEditCommandColumn>
                        <telerik:GridBoundColumn DataField="agentcode" DataType="System.Int64" FilterControlAltText="Filter agentcode column" HeaderText="agentcode" SortExpression="agentcode" UniqueName="agentcode">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>

                        <telerik:GridBoundColumn DataField="agentname" FilterControlAltText="Filter agentname column" HeaderText="agentname" SortExpression="agentname" UniqueName="agentname">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>
                        <telerik:GridBoundColumn DataField="sponsorcode" DataType="System.Int64" FilterControlAltText="Filter sponsorcode column" HeaderText="sponsorcode" SortExpression="sponsorcode" UniqueName="sponsorcode">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>

                        <telerik:GridBoundColumn DataField="FatherName" FilterControlAltText="Filter FatherName column" HeaderText="FatherName" SortExpression="FatherName" UniqueName="FatherName">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>
                        <telerik:GridBoundColumn DataField="HusbandName" FilterControlAltText="Filter HusbandName column" HeaderText="HusbandName" SortExpression="HusbandName" UniqueName="HusbandName">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>
                        <telerik:GridBoundColumn DataField="PhoneNo" FilterControlAltText="Filter PhoneNo column" HeaderText="PhoneNo" SortExpression="PhoneNo" UniqueName="PhoneNo">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>
                        <telerik:GridBoundColumn DataField="MobileNo" FilterControlAltText="Filter MobileNo column" HeaderText="MobileNo" SortExpression="MobileNo" UniqueName="MobileNo">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>

                        <telerik:GridBoundColumn DataField="Rank" DataType="System.Int32" FilterControlAltText="Filter Rank column" HeaderText="Rank" SortExpression="Rank" UniqueName="Rank">
                            <ColumnValidationSettings>
                                <ModelErrorMessage Text="" />
                            </ColumnValidationSettings>
                        </telerik:GridBoundColumn>


                    </Columns>
                    <EditFormSettings EditFormType="Template">
<EditColumn UniqueName="EditCommandColumn1" FilterControlAltText="Filter EditCommandColumn1 column"></EditColumn>
                        <FormTemplate>
                            <table class="auto-style1">
                                <tr>
                                  <td>Branch</td>
                                    <td>
                                      
                                        <telerik:RadComboBox ID="RadComboBox1" Runat="server" DataSourceID="SqlDataSource2" DataTextField="Name" DataValueField="Id" AutoPostBack="True" OnSelectedIndexChanged="RadComboBox1_SelectedIndexChanged">
                                        </telerik:RadComboBox>
                                       
                                    </td>
                                </tr>
                                <tr>
                                    <td>&nbsp;</td>
                                    <td>
                                        <asp:DropDownList ID="ddlAgent" runat="server">
                                        </asp:DropDownList>
                                    </td>
                                </tr>
                                <tr>
                                    <td>&nbsp;</td>
                                    <td>
                                        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource2" DataTextField="Name" DataValueField="Id" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
                                        </asp:DropDownList>
                                        <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" Text="ddl1" ControlToValidate="DropDownList1" ErrorMessage="RequiredFieldValidator" InitialValue="0"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                                <tr>
                                    <td>&nbsp;</td>
                                    <td>
                                        <asp:Button ID="Button1" runat="server" Text="Button" />
                                        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" Text="agent" ControlToValidate="ddlAgent" ErrorMessage="RequiredFieldValidator" InitialValue="0"></asp:RequiredFieldValidator>
                                    </td>
                                </tr>
                            </table>
                        </FormTemplate>
                    </EditFormSettings>
                </MasterTableView>
            </telerik:RadGrid>
            <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:relife_part2ConnectionString %>" SelectCommand="SELECT * FROM [agent]"></asp:SqlDataSource>
            <asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:relife_part2ConnectionString %>" SelectCommand="SELECT * FROM [tbl_companyMaster]"></asp:SqlDataSource>
        </div>




http://www.telerik.com/support/code-library/export-radgrid-content-to-excel-word-csv-pdf-with-ajax-enabled