2个以上dropdownlist进行互联（C#）

当需要一堆下拉框进行互联时，详见下文
例：当选择完医院时，自动对应该医院科室（本文最后附主要代码）在这里插入图片描述

首先写出一个下拉框的代码（记为dropdownlist1）
详情请见上一篇博客dropdownlis怎么使用
将dropdownlist1的属性AutoPostBack改为True
（千万别忘了，呜呜呜我就是忘了，然后研究了好久）
在前端双击dropdownlist1，然后在DropDownList1_SelectedIndexChange中写dropdownlist2的控制部分，以此类推在DropDownList2_SelectedIndexChange中写dropdownlist3的控制部分
遇到的问题
（1）查询到的数据有重复怎么办
其实这应该算是数据库知识了（但我当时忘记了），举个例子，我想在DropDownList2中展示以下第一列内容，但是you重复怎么办，只需要在select语句中加入DISTINCT就好啦。

代码如下

string queryRecord1;
queryRecord1 = "SELECT DISTINCT 列名 FROM 表名";

（2）dropdownlist1在选择完之后会立即变回默认值
这时就需要将你的dropdownlist1写在以下函数中,就好啦，注意要引用哦。

if(!IsPostBack)
{
你的dropdownlist1； 
}

最后附上开篇程序代码
前端（工具箱拖进来就好，别忘了改属性AutoPostBack）

 <div class="col-md-12"  >
        <asp:Label ID="Label1" runat="server" Text="请选择医院" style="font-size: large"></asp:Label>&nbsp;&nbsp;&nbsp;&nbsp
        <asp:DropDownList ID="DropDownList1" runat="server" Height="35px" Width="240px" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged"></asp:DropDownList>
        <br/><br/>
 </div>
 <div class="col-md-12"  
        <asp:Label ID="Label2" runat="server" Text="请选择科室" style="font-size: large"></asp:Label>&nbsp;&nbsp;&nbsp;&nbsp    
        <asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged"></asp:DropDownList>
        <asp:DropDownList ID="DropDownList3" runat="server"></asp:DropDownList>
 </div>

后端（我用的VS自带SQL数据库，不会的可见VS连接自带SQL数据库）

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

namespace 软件开发课程设计
{
    public partial class 挂号 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack) //防止返回默认值
            {
                cleckhospital();

            }
            
        }

        protected void cleckhospital()
        {
            string constr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
            SqlConnection conn = new SqlConnection(constr);
            conn.Open();
            string queryRecord;
            queryRecord = "SELECT hosname FROM hospital_log ";
            SqlCommand com;
            com = new SqlCommand(queryRecord, conn);
            SqlDataReader sqlreader;
            sqlreader = com.ExecuteReader();
            this.DropDownList1.DataSource = sqlreader;
            this.DropDownList1.DataTextField = "hosname";
            this.DropDownList1.DataValueField = "hosname";
            this.DropDownList1.DataBind();
            this.DropDownList1.Items.Insert(0, new ListItem("<--请选择医院-->", "0"));//设置默认值
            this.DropDownList2.Items.Insert(0, new ListItem("<--请选择分类-->", ""));
            this.DropDownList3.Items.Insert(0, new ListItem("<--请选择科室-->", ""));
            sqlreader.Close();
        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {              
               string constr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
                SqlConnection conn = new SqlConnection(constr);
                conn.Open();
                string queryRecord1;
                queryRecord1 = "SELECT DISTINCT lall FROM wuxi_people";
                SqlCommand com1;
                com1 = new SqlCommand(queryRecord1, conn);
                SqlDataReader sqlreader1;
                sqlreader1 = com1.ExecuteReader();
                this.DropDownList2.DataSource = sqlreader1;
                this.DropDownList2.DataTextField = "lall";
                this.DropDownList2.DataValueField = "lall";
                this.DropDownList2.DataBind();             
                sqlreader1.Close();
        }

        protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
        {
            string constr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
            SqlConnection conn = new SqlConnection(constr);
            conn.Open();
            string queryRecord1;
            queryRecord1 = "SELECT  branch FROM wuxi_people where lall=N'" + DropDownList2.SelectedItem.Text + "' ;";
            SqlCommand com1;
            com1 = new SqlCommand(queryRecord1, conn);
            SqlDataReader sqlreader1;
            sqlreader1 = com1.ExecuteReader();
            this.DropDownList3.DataSource = sqlreader1;
            this.DropDownList3.DataTextField = "branch";
            this.DropDownList3.DataValueField = "branch";
            this.DropDownList3.DataBind();
            sqlreader1.Close();
        }
    }
}

2个以上dropdownlist进行互联（C#）

猜你喜欢