从gridview获取row null

Question

当我尝试调试时，我看到我的按钮为空。谁知道为什么？这是代码。提前谢谢！

protected void Delete_Click(object sender, EventArgs e)
{
    con.Open();
    Button btn = sender as Button;
    GridViewRow row = (GridViewRow)btn.NamingContainer;
    Label headerAthleteID = (Label)row.FindControl("lblAthleteID");
    con.Close();
}

这是我的网格视图部分

         <asp:TemplateField SortExpression="deleteColumn">
             <ItemTemplate>
                <asp:Button ID ="deleteButton" runat="server" Text="Delete" OnClick="Delete_Click" />
             </ItemTemplate>
         </asp:TemplateField>