ASP.net & C# - 当前上下文中不存在控件，designer.cs 不存在

Question

这与我正在从事的项目有关。我的表格几乎都放在一起了。每个下拉列表都将正确填充并相互馈送。现在我只需要获取表单以将插入查询发送回数据库。当我简单地单击数据库中的 "Insert" 按钮时，我收到一条错误消息，指出“无法将值 NULL 插入列 'Issue_ID'、table 'NintendoPowerPoll.dbo.Poll_Results'；列不允许空值。INSERT 失败。声明已终止。"

我已经发现这意味着每个字段的选定值没有被输入到查询中。因此，我开始尝试在 *.asp.cs 文件中为“插入”按钮设置代码，这样站点将运行插入查询，从所选字段中提取必要的信息。但是，当我尝试让查询从 IssueDateDropDownList 提供 .SelectedItem.Value 时，Visual Studio 2013 在控件名称下给出了一条错误消息，该消息显示为 "The Name IssueDateDropDownList does not exist in the current context." 这里的进一步研究表明这是 Designer.cs 文件的问题...只是该文件在解决方案资源管理器的项目文件列表中不可见。我还能做些什么来解决这个问题吗？

ASP 站点：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="ResultsEntryForm.aspx.cs" Inherits="ResultsEntryForm" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="ResultsDataEntryForm" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server" AllowPaging="True" 
            AutoGenerateColumns="False" DataSourceID="PollResultsDataSource" 
            AllowSorting="True">
            <Columns>
                <asp:BoundField DataField="Issue_Date" HeaderText="Issue_Date" 
                    SortExpression="Issue_Date" />
                <asp:BoundField DataField="Platform_Type" HeaderText="Platform_Type" 
                    SortExpression="Platform_Type" />
                <asp:BoundField DataField="Element_Title" HeaderText="Element_Title" 
                    SortExpression="Element_Title" />
                <asp:BoundField DataField="Poll_Score" HeaderText="Poll_Score" 
                    SortExpression="Poll_Score" />
            </Columns>
        </asp:GridView>
        <asp:FormView ID="ResultsFormView" runat="server" AllowPaging="True" 
            DataSourceID="PollResultsDataSource">
            <InsertItemTemplate>
                Issue_Date:
                <asp:DropDownList ID="IssueDateDropDownList" runat="server" AutoPostBack="True" 
                    DataSourceID="IssueDateDropDownDataSource" DataTextField="Issue_Date" 
                    DataValueField="Issue_ID" 
                    SelectedValue='<%# Bind("Issue_Date", "{0:d}") %>'>
                </asp:DropDownList>
                <br />
                Platform_Type:
                <asp:DropDownList ID="PlatformDropDownList" runat="server" 
                    DataSourceID="PlatformDropDownDataSource" DataTextField="Platform_Type" 
                    DataValueField="Platform_ID" AutoPostBack="True">
                </asp:DropDownList>
                <br />
                Element_Title:
                <asp:DropDownList ID="TitleDropDownList" runat="server" AutoPostBack="True" 
                    DataSourceID="GameSqlDataSource" DataTextField="Element_Title" 
                    DataValueField="Element_Group_ID">
                </asp:DropDownList>
                <br />
                Poll_Score:
                <asp:TextBox ID="ScoreTextBox" runat="server"></asp:TextBox>
                <br />
                <asp:LinkButton ID="InsertButton" runat="server" CausesValidation="True" 
                    CommandName="Insert" Text="Insert" ValidationGroup="Insert" 
                    OnClick="InsertButton_Click" />
                &nbsp;
                <asp:LinkButton ID="InsertCancelButton" runat="server" 
                    CausesValidation="False" CommandName="Cancel" Text="Cancel" />
                <asp:SqlDataSource ID="GameSqlDataSource" runat="server" 
                    ConnectionString="<%$ ConnectionStrings:NintendoPowerPollConnectionString %>" 
                    SelectCommand="SELECT [Element_Group_ID], [Element_Title] FROM [na_Games] WHERE ([Platform_ID] = @Platform_ID)">
                    <SelectParameters>
                        <asp:ControlParameter ControlID="PlatformDropDownList" Name="Platform_ID" 
                            PropertyName="SelectedValue" Type="Int32" />
                    </SelectParameters>
                </asp:SqlDataSource>
            </InsertItemTemplate>
            <ItemTemplate>
                Issue_Date:
                <asp:Label ID="Issue_DateLabel" runat="server" 
                    Text='<%# Bind("Issue_Date") %>' />
                <br />
                Platform_Type:
                <asp:Label ID="Platform_TypeLabel" runat="server" 
                    Text='<%# Bind("Platform_Type") %>' />
                <br />
                Element_Title:
                <asp:Label ID="Element_TitleLabel" runat="server" 
                    Text='<%# Bind("Element_Title") %>' />
                <br />
                Poll_Score:
                <asp:Label ID="Poll_ScoreLabel" runat="server" 
                    Text='<%# Bind("Poll_Score") %>' />
                <br />
                <asp:LinkButton ID="EditButton" runat="server" CausesValidation="False" 
                    CommandName="Edit" Text="Edit" />
                &nbsp;<asp:LinkButton ID="NewButton" runat="server" CausesValidation="False" 
                    CommandName="New" Text="New" />
            </ItemTemplate>
        </asp:FormView>
    </div>
    <asp:SqlDataSource ID="PollResultsDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:NintendoPowerPollConnectionString %>" 
        InsertCommand="INSERT INTO Poll_Results(Issue_ID, Element_Group_ID, Poll_Score) VALUES (@Issue_ID, @Element_Group_ID, @Poll_Score)" 
        SelectCommand="SELECT NintendoPowerIssue.Issue_Date, na_lkpPlatformTypes.Platform_Type, na_Games.Element_Title, Poll_Results.Poll_Score 
            FROM Poll_Results INNER JOIN NintendoPowerIssue ON Poll_Results.Issue_ID = NintendoPowerIssue.Issue_ID 
            INNER JOIN na_Games ON Poll_Results.Element_Group_ID = na_Games.Element_Group_ID 
            INNER JOIN na_lkpPlatformTypes ON na_Games.Platform_ID = na_lkpPlatformTypes.Platform_ID" 
        UpdateCommand="UPDATE Poll_Results SET Poll_Score = @Poll_Score 
            FROM Poll_Results 
            INNER JOIN na_Games ON Poll_Results.Element_Group_ID = na_Games.Element_Group_ID 
            INNER JOIN NintendoPowerIssue ON Poll_Results.Issue_ID = NintendoPowerIssue.Issue_ID 
            WHERE (Poll_Results.Issue_ID = @Issue_ID) AND (Poll_Results.Element_Group_ID = @Element_Group_ID)">
        <InsertParameters>
            <asp:Parameter Name="Issue_ID" />
            <asp:Parameter Name="Element_Group_ID" />
            <asp:Parameter Name="Poll_Score" />
        </InsertParameters>
        <UpdateParameters>
            <asp:Parameter Name="Poll_Score" />
            <asp:Parameter Name="Issue_ID" />
            <asp:Parameter Name="Element_Group_ID" />
        </UpdateParameters>
    </asp:SqlDataSource>
    <asp:SqlDataSource ID="IssueDateDropDownDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:NintendoPowerPollConnectionString %>" 
        SelectCommand="SELECT [Issue_ID], [Issue_Date] FROM [NintendoPowerIssue]">
    </asp:SqlDataSource>
    <asp:SqlDataSource ID="PlatformDropDownDataSource" runat="server" 
        ConnectionString="<%$ ConnectionStrings:NintendoPowerPollConnectionString %>" 
        SelectCommand="SELECT [Platform_ID], [Platform_Type] FROM [na_lkpPlatformTypes] WHERE [Platform_ID] IN (SELECT DISTINCT [Platform_ID] FROM [na_Games])" />
    </form>
</body>
</html>

C# 后页：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

public partial class ResultsEntryForm : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    private DataTable BindDropDownList(string field)
    {
        DataTable dt = new DataTable();
        SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["NintendoPowerPollConnectionString"].ToString());
        try
        {
            connection.Open();
            string sqlStatement = "SELECT [Element_Group_ID], [Element_Title] FROM [na_Games] WHERE ([Platform_ID] = @Platform_ID)";
            SqlCommand sqlCmd = new SqlCommand(sqlStatement, connection);
            SqlDataAdapter sqlDa = new SqlDataAdapter(sqlCmd);
            sqlCmd.Parameters.AddWithValue("@Platform_ID", field);
            sqlDa.Fill(dt);
        }
        catch (System.Data.SqlClient.SqlException ex)
        {
            Server.ClearError();
            Response.Write(ex.Message + ("<br />") + ex.Source);
        }
        finally
        {
            connection.Close();
        }

        return dt;
    }
    protected void InsertButton_Click(object sender, EventArgs e)
    {
        SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["NintendoPowerPollConnectionString"].ToString());
        Int32 IssueID = Convert.ToInt32(IssueDateDropDownList.SelectedItem.Value);
        try
        {
            connection.Open();
        }
    }
}

我需要删除 BindDropDownList 代码，因为它不需要，但我认为这与手头的问题无关。

Answer 1

如果代码最初是用旧版本的 VS 编写的，可能是因为 VS 2013 在不同的地方期望的东西。

看这里：The name 'control' does not exist in the current context

此外 ASP WebForms 没有 designer.cs class。但是每个页面（aspx class）下面都有一个 *.aspx.cs 文件和一个 *.aspx.designer.cs 文件。（其中 x）是页面的名称。如果它们不存在，则说明您的项目结构有问题。

Answer 2

所以，我找出了导致问题的原因。因为有问题的下拉框位于表单模板中（特别是在 FormView 的插入模板下），所以有问题的脚本无法 "see" 有问题的下拉列表。当我在表单视图之外重新创建插入表单时，它能够 "see" 必要的控件。问题不在于 C# 代码，而在于网站前端的结构。

ASP.net & C# - 当前上下文中不存在控件，designer.cs 不存在

ASP.net & C# - The Control does not exist in the current context, designer.cs doesn't exist

c#

sql-server

asp.net

visual-studio-2013