How to find textbox control inside gridview footer

  How to find textbox control inside gridview footer

 C# code :
     TextBox YourTxtBoxName= (TextBox)GridView1.FooterRow.FindControl("FooterTextBox");

 Gridview :
  <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" EmptyDataText="There are no data records to display." ShowFooter="True">
            <Columns>
                <asp:TemplateField HeaderText="Subject" SortExpression="Subject">
                    <EditItemTemplate>
                        <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("col_Name") %>'></asp:TextBox>
                    </EditItemTemplate>
                    <FooterTemplate>
                        <asp:TextBox ID="FooterTextBox" runat="server" Width="77px"></asp:TextBox>
                        <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Add" />
                    </FooterTemplate>
                    <ItemTemplate>
                        <asp:Label ID="Label1" runat="server" Text='<%# Bind("col_Name") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>