I am getting an error when i call the button id which is inside GridView Item template.

Error: "The TargetControlID of 'mpueResend' is not valid. A control with ID 'btnResend' could not be found."

Code:

Code:
<asp:GridView ID="GridMultiD" runat="server" CellPadding="3" 
                        AlternatingRowStyle-BackColor="#EDF3F7" HeaderStyle-CssClass="gridbgheading" 
                        Width="100%" HeaderStyle-HorizontalAlign="Center" >
                        
                    
                    <Columns>
                        <asp:TemplateField HeaderText="Resend">
                            <ItemStyle HorizontalAlign="Center" />
                                <ItemTemplate>
                                    <asp:Button ID="btnResend" runat="server" Text="Resend" CssClass="text ButtonInline"  />
                                </ItemTemplate>
                        </asp:TemplateField>
                        </Columns>
                        
                    </asp:GridView>
Code:
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<asp:ModalPopupExtender ID="mpueResend" runat="server" TargetControlID="btnResend" PopupControlID="pnlPopupResend" 
        BackgroundCssClass="modalBackGround" DropShadow="true" CancelControlID="btnCancelR" >
    </asp:ModalPopupExtender>
Please let me know if there is any solution for this.

Thank You.