本文介绍了一个使用ASP.NET实现的DropDownList控件联动选择功能的例子。通过C#后端代码，从数据库获取数据并填充两个下拉列表，实现根据大类自动更新小类选项的功能。
<%...@Pagelanguage="c#"Codebehind="WebForm1.aspx.cs"AutoEventWireup="false"Inherits="mytest.WebForm1"%>
<!DOCTYPEHTMLPUBLIC"-//W3C//DTDHTML4.0Transitional//EN"><HTML><HEAD><title>WebForm1</title><metaname="GENERATOR"Content="MicrosoftVisualStudio.NET7.1"><metaname="CODE_LANGUAGE"Content="C#"><metaname="vs_defaultClientScript"content="JavaScript"><metaname="vs_targetSchema"content="http://schemas.microsoft.com/intellisense/ie5"><script>...
vararry=newArray();<%for(inti=0;i<cdt.Rows.Count;i++)
...{%>arry[<%=i%>]=newArray("<%=cdt.Rows[i]["d_id"]%>","<%=cdt.Rows[i]["subname"]%>","<%=cdt.Rows[i]["sub_id"]%>");//注意这里的Array的使用，里面有三个下标，第一个下标索引为0<%
}%>functionbindsub(value)...{document.getElementById("dlsmall").length=0;for(vari=0;i<arry.length;i++)...{if(arry[i][0]==value)//重点：用于判断是不是选中的大类所对应的小类...{document.getElementById("dlsmall").options.add(newOption(arry[i][1],arry[i][2]));//arry[i][1]指arry数组里的下标为１的元素值}}}
</script></HEAD><bodyMS_POSITIONING="GridLayout"><formid="Form1"method="post"runat="server"><FONTface="宋体"><asp:DropDownListid="dlbig"style="Z-INDEX:101;LEFT:296px;POSITION:absolute;TOP:192px"runat="server"></asp:DropDownList><asp:DropDownListid="dlsmall"style="Z-INDEX:102;LEFT:440px;POSITION:absolute;TOP:192px"runat="server"></asp:DropDownList><asp:Buttonid="Button1"style="Z-INDEX:103;LEFT:376px;POSITION:absolute;TOP:264px"runat="server"Text="Button"></asp:Button><asp:Labelid="Label1"style="Z-INDEX:104;LEFT:296px;POSITION:absolute;TOP:80px"runat="server"Width="312px"ForeColor="Red">Label</asp:Label></FONT></form></body></HTML>
cs代码如下:
usingSystem;usingSystem.Collections;usingSystem.ComponentModel;usingSystem.Data;usingSystem.Drawing;usingSystem.Web;usingSystem.Web.SessionState;usingSystem.Web.UI;usingSystem.Web.UI.WebControls;usingSystem.Web.UI.HtmlControls;usingSystem.Configuration;usingSystem.Data.SqlClient;namespacemytest...{/**////<summary>///WebForm1的摘要说明。///</summary>publicclassWebForm1:System.Web.UI.Page...{privatereadonlystringconnstr=ConfigurationSettings.AppSettings["connstr"].ToString();protectedSystem.Web.UI.WebControls.DropDownListdlbig;protectedSystem.Web.UI.WebControls.DropDownListdlsmall;protectedSystem.Web.UI.WebControls.ButtonButton1;protectedSystem.Web.UI.WebControls.LabelLabel1;protectedDataTablecdt;//这里是html页面中要用到的datatable对象，所以必须将其设为公共的privatevoidPage_Load(objectsender,System.EventArgse)...{if(!Page.IsPostBack)...{cdt=GetTB("select*fromsubunionaddress");this.dlbig.Attributes.Add("onchange","bindsub(this.value)");bindbig();}}privatevoidbindbig()...{stringsql="select*fromunionaddress";DataTabledt=GetTB(sql);this.dlbig.DataTextField="name";this.dlbig.DataValueField="d_id";this.dlbig.DataSource=dt;this.dlbig.DataBind();}privateDataTableGetTB(stringsql)...{SqlConnectionmyconn=newSqlConnection(connstr);SqlDataAdapteradpt=newSqlDataAdapter(sql,myconn);DataSetds=newDataSet();adpt.Fill(ds);return(DataTable)ds.Tables[0];}Web窗体设计器生成的代码#regionWeb窗体设计器生成的代码overrideprotectedvoidOnInit(EventArgse)...{////CODEGEN:该调用是ASP.NETWeb窗体设计器所必需的。//InitializeComponent();base.OnInit(e);}/**////<summary>///设计器支持所需的方法-不要使用代码编辑器修改///此方法的内容。///</summary>privatevoidInitializeComponent()...{this.Button1.Click+=newSystem.EventHandler(this.Button1_Click);this.Load+=newSystem.EventHandler(this.Page_Load);}#endregionprivatevoidButton1_Click(objectsender,System.EventArgse)...{stringbig=dlbig.SelectedValue.ToString();stringnobig=dlsmall.SelectedValue.ToString();stringsmall=Request.Form["dlsmall"].ToString();//this.Label1.Text="当前你选定的是"+big.ToString()+"地区,"+small.ToString()+"市";}}}
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