当前上下文中不存在名称 gridview1

我是 C# 新手。只需遵循 YouTube 简单示例并尝试简单地连接到 SQL 数据库。但GridView1给我一个错误。 这是我的 WebForm1.aspx.cs

using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data.OleDb;
using System.Data.Odbc;



namespace adoDemo
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            String CS = "data source =.; database = AdventureWorks2016CTP3; integrated security = SSPI";
            SqlConnection con = new SqlConnection(CS);
            SqlCommand cmd = new SqlCommand("select top 5 * from [Sales].[CreditCard]", con);
            con.Open();
            GridView1.DataSource = cmd.ExecuteReader();
            GridView1.DataBind();
            con.Close();
        }
    }
}

这是WebForm.aspx.designer.cs

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated. 
// </auto-generated>
//------------------------------------------------------------------------------

namespace adoDemo {


    public partial class WebForm1 
    {

        /// <summary>
        /// form1 control.
        /// </summary>
        /// <remarks>
        /// Auto-generated field.
        /// To modify move field declaration from designer file to code-behind file.
        /// </remarks>
        protected global::System.Web.UI.HtmlControls.HtmlForm form1;
    }
}

这是WebForm1.aspx

   <script runat="server">

    Protected Sub Unnamed1_SelectedIndexChanged(sender As Object, e As EventArgs)

    End Sub
</script>
body 

<asp:gridview id="GridView1" runat="server" OnSelectedIndexChanged="Unnamed1_SelectedIndexChanged" BackColor="#DEBA84" BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px" CellPadding="3" CellSpacing="2">
    <FooterStyle BackColor="#F7DFB5" ForeColor="#8C4510" />
    <HeaderStyle BackColor="#A55129" Font-Bold="True" ForeColor="White" />
    <PagerStyle ForeColor="#8C4510" HorizontalAlign="Center" />
    <RowStyle BackColor="#FFF7E7" ForeColor="#8C4510" />
    <SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="White" />
    <SortedAscendingCellStyle BackColor="#FFF1D4" />
    <SortedAscendingHeaderStyle BackColor="#B95C30" />
    <SortedDescendingCellStyle BackColor="#F1E5CE" />
    <SortedDescendingHeaderStyle BackColor="#93451F" />
</asp:gridview>

这就是我的WebForm1.aspx.designer.cs好像

Is there anything I'm missing?

页面设计者有时确实会拒绝向 .designer.cs 文件添加控件；我已经见过很多次了。

如果发生这种情况，请自行将类级变量添加到 .aspx.cs 中：-

namespace adoDemo
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        // make sure its's the same spelling & case as in the .aspx
        protected GridView GridView1;

        protected void Page_Load(object sender, EventArgs e)
        {
            // etc
        }
    }
}