ASP.NET DEMOⅠ:联动下来框(DropDownList)

最新推荐文章于 2020-06-13 11:52:55 发布

p是马甲

最新推荐文章于 2020-06-13 11:52:55 发布

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CC 4.0 BY-SA版权

文章标签： xhtml 数据库 c#

原文链接：http://www.cnblogs.com/Jinglecat/archive/2007/05/29/763245.html

本文通过实例演示了ASP.NET中DropDownList控件的多种使用方法，包括页面声明式、代码绑定式及代码添加式填充数据源，并介绍了如何实现联动效果。

开篇废话～

也算序
下了个大胆的决定：整理出一系列 ASP.NET 实践相关的示例，来源大部分都是网络收集，然而都是自己实践总结。

约定：
1.环境：ASP.NET 2.0。尽量提供 1.x 的相关信息
2.编码方式：内联代码。优势是，简洁，方便测试，只需要一张 .aspx 页面
3.＋

那就开始吧～

DEMOⅠ:联动下来框(DropDownList)

提示：服务端版本，虽然当前AJAX盛行，然而，凡事都需要一个过程，对于ASP.NET初学者，有助于加深对DropDownList（下文缩写为DRP）的理解。如果，您需要无刷新版本，不想浪费您宝贵时间，请跳过:->

目的：实现四联动，分别展示三种如何给DRP添加数据源的方法，外加说明为什么你的DRP就是不会保持选择状态（应该在 IsPostBack 内绑定数据）：

1. 页面声名式: drpCountry

2. 代码绑定式: drpProvince, drpCity

3. 代码添加式: drpDistrict

技巧：

1.一般页面初始化过程的绑定数据，最好放在 IsPostBack 内，这样页面回发（PostBack）的时候就不会再执行一次

 
void Page_Load(object sender, EventArgs e) 
{ 
    if (!IsPostBack) { 
        // Load default Provinces and Cities. 
        LoadProvinceData(); 
        LoadCityData(); 
        LoadDistrictData(); 
    } 
} 
  

2.实现自动联动的关键是要让DRP选择项改变的时候，自动回发页面，设置其 AutoPostBack="true" ，然后实现SelectedIndexChanged 事件的处理程序

 
City:<asp:DropDownList ID="drpCity" DataTextField="CityName" DataValueField="CityId" runat="server" ="true" OnSelectedIndexChanged="drpCity_SelectedIndexChanged">         
</asp:DropDownList>

3. 对于 ASP.NET 2.0，DRP 新增一个属性 AppendDataBoundItems，该属性接受一个bool值，指示是否在绑定前清楚已有的Items。默认值为false，即先清除。

 
Province:<asp:DropDownList ID="drpProvince" ="true" DataTextField="ProvinceName" DataValueField="ProvinceId" AutoPostBack="true" OnSelectedIndexChanged="drpProvince_SelectedIndexChanged" runat="server">         
    </asp:DropDownList>

 
<%@ Page Language="C#" %> 
<%@ Import Namespace="System.Data" %> 
  
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
  
<script runat="server">

  
    void Page_Load(object sender, EventArgs e) 
    { 
        if (!IsPostBack) { 
            // Load default Provinces and Cities. 
            LoadProvinceData(); 
            LoadCityData(); 
            LoadDistrictData(); 
        } 
    } 
  
    #region event handler(s) 
  
    void drpCountry_SelectedIndexChanged(object sender, EventArgs e) 
    { 
        LoadProvinceData(); 
        LoadCityData(); 
        LoadDistrictData(); 
    }    
     
    void drpProvince_SelectedIndexChanged(object sender, EventArgs e) 
    { 
        LoadCityData(); 
        LoadDistrictData(); 
    } 
  
    void drpCity_SelectedIndexChanged(object sender, EventArgs e) 
    { 
        LoadDistrictData(); 
    } 
  
    #endregion 
     
    #region private helpers 
  
    void LoadProvinceData() 
    { 
        DataTable dtProvince = new DataTable();// null; 
         
        // In this demo, we just provider provinces for Chinese 
        if (drpCountry.SelectedValue.ToLower() == "cn") { 
            // In your case, maybe you like to populate the Province data  
            // from the back-end datastore such as database.         
            dtProvince = CreateProvinceTable(); 
        } 
         
        drpProvince.DataSource = dtProvince; 
        drpProvince.DataBind(); 
    } 
  
    void LoadCityData() 
    { 
        // In your case, maybe you perform the search in your database 
        // by ADO.NET with inner-sql or stored procedure. 
        DataTable dtCity = CreateCityTable(); 
        DataView dvCity = dtCity.DefaultView; 
        // Providers a dummy ProvincId when there are none of provinces to select. 
        string selectedProvinceId = (drpProvince.SelectedValue.Length != 0) ? drpProvince.SelectedValue : "-1"; 
        dvCity.RowFilter = "ProvinceID=" + selectedProvinceId; 
         
        drpCity.DataSource = dvCity; 
        drpCity.DataBind(); 
    } 
  
    void LoadDistrictData() 
    {         
        // Clears the items 
        drpDistrict.Items.Clear(); 
         
        // In this demo, we just only provider districts for Chongqing city. 
        if (drpCity.SelectedValue != "5") return; 
         
        // 
        ListItem item = null;         
         
        // 
        item = new ListItem("Shapingba", "1"); 
        drpDistrict.Items.Add(item); 
        // 
        item = new ListItem(); 
        item.Text = "Yuzhongqu"; 
        item.Value = "2"; 
        item.Selected = true; 
        drpDistrict.Items.Add(item); 
        // 
        drpDistrict.Items.Add(new ListItem("Jiangbei", "3")); 
    } 
  
    #endregion 
  
    #region Creates Sample Data below. 
  
    DataTable CreateProvinceTable() 
    { 
        DataTable dt = new DataTable(); 
        dt.Columns.Add("ProvinceID", typeof(int)); 
        dt.Columns.Add("ProvinceName", typeof(string)); 
  
        DataRow row = dt.NewRow(); 
        row.ItemArray = new object[] {1, "Jiangsu"}; 
        dt.Rows.Add(row); 
  
        row = dt.NewRow(); 
        row["ProvinceID"] = 2; 
        row["ProvinceName"] = "Fujian"; 
        dt.Rows.Add(row); 
         
        row = dt.NewRow(); 
        row[0] = 3; 
        row[1] = "Chongqing"; 
        dt.Rows.Add(row); 
  
        return dt;         
    } 
  
    DataTable CreateCityTable() 
    { 
        DataTable dt = new DataTable(); 
        dt.Columns.Add("CityID", typeof(int)); 
        dt.Columns.Add("CityName", typeof(string)); 
        dt.Columns.Add("ProvinceID", typeof(int)); 
  
        DataRow row = dt.NewRow(); 
        row.ItemArray = new object[]{1, "Nanjiang", 1}; 
        dt.Rows.Add(row); 
  
        row = dt.NewRow(); 
        row.ItemArray = new object[]{2, "Nanchong", 1}; 
        dt.Rows.Add(row); 
  
        row = dt.NewRow(); 
        row.ItemArray = new object[] { 3, "Fuzhou", 2 }; 
        dt.Rows.Add(row); 
  
        row = dt.NewRow(); 
        row.ItemArray = new object[] { 4, "Quanzhou", 2 }; 
        dt.Rows.Add(row); 
         
        row = dt.NewRow(); 
        row.ItemArray = new object[] { 5, "Chongqing", 3}; 
        dt.Rows.Add(row); 
  
        return dt; 
    } 
  
    #endregion 
     
   </
   script
   > 
  
<html xmlns="http://www.w3.org/1999/xhtml" > 
<head runat="server"> 
    <title>ASP.NET Demo 1:DropDownList</title> 
</head> 
<body> 
    <form id="form1" runat="server"> 
    <div> 
    Country:<asp:DropDownList ID="drpCountry" runat="server" AutoPostBack="true" OnSelectedIndexChanged="drpCountry_SelectedIndexChanged"> 
        <asp:ListItem Value="cn">Chinese</asp:ListItem>         
        <asp:ListItem Value="uk">U.K</asp:ListItem> 
        <asp:ListItem Value="us">U.S.A</asp:ListItem> 
    </asp:DropDownList> 
    Province:<asp:DropDownList ID="drpProvince" DataTextField="ProvinceName" DataValueField="ProvinceId" AutoPostBack="true" OnSelectedIndexChanged="drpProvince_SelectedIndexChanged" runat="server">         
    </asp:DropDownList> 
    City:<asp:DropDownList ID="drpCity" DataTextField="CityName" DataValueField="CityId" runat="server" AutoPostBack="true" OnSelectedIndexChanged="drpCity_SelectedIndexChanged">         
    </asp:DropDownList> 
    District:<asp:DropDownList ID="drpDistrict" runat="server"></asp:DropDownList> 
    </div> 
    </form> 
</body> 
</html> 
  