Question

我是C＃的新手。我正在尝试创建一个Web应用程序，允许用户根据他们从下拉列表中选择的主题查看类。我所拥有的代码并未向用户显示他们从下拉列表中选择的信息。无论选择哪个选项，它都会显示相同的gridview数据。

这是显示Web应用程序的代码。

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

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
 <head runat="server">
    <title>Summer 2016</title>
 </head>
 <body>
     <form id="form1" runat="server">
     <div>
     <h1>Summer 2016</h1>
         <h2>Classes offered</h2>
         <h3>Please Choose a Subject</h3>
     </div>
         <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource1" DataTextField="Subjects" DataValueField="Subjects">
         </asp:DropDownList>
         <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:RegistrationConnectionString %>" SelectCommand="SELECT [Subject], [Id] FROM [Classes]"></asp:SqlDataSource>
         <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="Id" DataSourceID="SqlDataSource2">
             <Columns>
                 <asp:BoundField DataField="Id" HeaderText="Id" ReadOnly="True" SortExpression="Id" />
                 <asp:BoundField DataField="Instrutor" HeaderText="Instrutor" SortExpression="Instrutor" />
                 <asp:BoundField DataField="CRN" HeaderText="CRN" SortExpression="CRN" />
                 <asp:BoundField DataField="Credits" HeaderText="Credits" SortExpression="Credits" />
                 <asp:BoundField DataField="Day" HeaderText="Day" SortExpression="Day" />
                 <asp:BoundField DataField="Time" HeaderText="Time" SortExpression="Time" />
                 <asp:BoundField DataField="Title" HeaderText="Title" SortExpression="Title" />
                 <asp:BoundField DataField="Section" HeaderText="Section" SortExpression="Section" />
                 <asp:BoundField DataField="Location" HeaderText="Location" SortExpression="Location" />
                 <asp:BoundField DataField="BeginEnd" HeaderText="BeginEnd" SortExpression="BeginEnd" />
                 <asp:BoundField DataField="Number" HeaderText="Number" SortExpression="Number" />
                 <asp:BoundField DataField="SubjectId_Fk" HeaderText="SubjectId_Fk" SortExpression="SubjectId_Fk" />
             </Columns>
         </asp:GridView>
         <asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:RegistrationConnectionString %>" SelectCommand="SELECT [Id], [Instrutor], [CRN], [Credits], [Day], [Time], [Title], [Section], [Location], [BeginEnd], [Number], [SubjectId_Fk] FROM [Classes]"></asp:SqlDataSource>
         <br />
     </form>
 </body>
 </html>

这是Web应用程序背后的代码。

enter code here
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
using System.Configuration;
public partial class Summer : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
           // DropDownList1.DataSource = GetDataTable();
            DropDownList1.DataValueField = "Id";
            DropDownList1.DataTextField = "Subject";
            DropDownList1.DataBind();
        }
    }

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
            using (SqlConnection Cn = new SqlConnection(ConfigurationManager.ConnectionStrings[@"C:\Users\Keith\Documents\Registration.mdf"].ConnectionString))
            {
             using (SqlCommand Cmd = new SqlCommand("select * from Classes where Id=" + DropDownList1.SelectedValue.ToString(), Cn))
            {
            Cn.Open();

                Cmd.Parameters.AddWithValue("@Id", int.Parse(DropDownList1.SelectedValue));
                SqlDataReader Dr = Cmd.ExecuteReader();
                if (Dr.HasRows)
                {
                    GridView1.DataSource = Dr;
                    GridView1.DataBind();
                }
                Dr.Close();

                Cn.Close();
            }

        }
    }
    public static DataTable GetDataTable(string sqlCommand)
    {
        DataTable table = new DataTable();
        try
        {
             using (SqlConnection myConnection = new SqlConnection(ConfigurationManager.ConnectionStrings[@"C:\Users\Keith\Documents\Registration.mdf"].ConnectionString))
            {
                using (SqlCommand cmd = new SqlCommand(sqlCommand, myConnection))
                {
                    using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
                    {
                        adapter.Fill(table);
                    }
                }
            }
        }
        catch (Exception ex)
        {
            table = null;
            throw ex;
        }
        return table;
    }
}

Answer 1

更新Dropdown元素，如下所示，

<asp:DropDownList ID="DropDownList1" 

runat="server" AutoPostBack="True" 

DataSourceID="SqlDataSource1" DataTextField="Subjects" 

DataValueField="Subjects" 

onselectedindexchanged="DropDownList1_SelectedIndexChanged">

     </asp:DropDownList>

我的Web应用程序中的gridview数据与从下拉列表中选择的选择不对应

1 个答案: