回调实现无刷新级联下拉框

wayne23

于 2008-01-22 14:56:00 发布

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分类专栏： .NET 文章标签： server string asp database function 产品

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以northwind数据库为例。选择分类下拉框的一项后，无刷新更改产品下拉框的显示

前台代码：

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

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

<head runat="server">

<title>无标题页</title>

<script type="text/javascript">

function CallServer(args,context)

{

context.innerHTML = "Loading...";

<%= ClientScript.GetCallbackEventReference(this,"args","GetServerData","context") %>

}

function GetServerData(result,context)

{

context.innerHTML = result;

}

</script>

</head>

<body>

<form id="form1" runat="server">

<div>

<asp:DropDownList ID="ddlCategory" runat="server"></asp:DropDownList>

<span id="pnlProduct">

<asp:DropDownList ID="ddlProduct" runat="server"></asp:DropDownList>

</span>

</div>

</form>

</body>

</html>

后台代码：

using System;

using System.Data;

using System.Data.SqlClient;

using System.IO;

using System.Configuration;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page,ICallbackEventHandler

{

protected string callbackResult;

protected void Page_Load(object sender, EventArgs e)

{

if (!IsPostBack)

{

BindToCategory();

this.ddlCategory.Attributes.Add("onchange", "CallServer(this.value,pnlProduct)");

this.ddlProduct.Items.Add(new ListItem("--产品--", "-1"));

}

}

/// <summary>

/// 绑定分类

/// </summary>

private void BindToCategory()

{

SqlConnection conn = new SqlConnection("Server=(local);database=northwind;uid=sa;pwd=123");

SqlDataAdapter sda = new SqlDataAdapter("SELECT categoryID,categoryName FROM categories", conn);

DataTable dt = new DataTable();

sda.Fill(dt);

this.ddlCategory.DataSource = dt;

this.ddlCategory.DataTextField = "categoryName";

this.ddlCategory.DataValueField = "categoryID";

this.ddlCategory.DataBind();

this.ddlCategory.Items.Insert(0, new ListItem("--分类--", "-1"));

}

private void BindToProduct(int categoryID)

{

SqlConnection conn = new SqlConnection("Server=(local);database=northwind;uid=sa;pwd=123");

SqlDataAdapter sda = new SqlDataAdapter("SELECT productID,productName FROM products WHERE categoryID=" + categoryID, conn);

DataTable dt = new DataTable();

sda.Fill(dt);

this.ddlProduct.DataSource = dt;

this.ddlProduct.DataTextField = "productName";

this.ddlProduct.DataValueField = "productID";

this.ddlProduct.DataBind();

if (ddlProduct.Items.Count == 0)

{

this.ddlProduct.Items.Add(new ListItem("--产品--", "-1"));

}

}

private string RenderElement(Control control)

{

StringWriter writer = new StringWriter();

HtmlTextWriter output = new HtmlTextWriter(writer);

control.RenderControl(output);

output.Flush();

output.Close();

string htmlCode = writer.ToString();

writer.Close();

return htmlCode;

}

void ICallbackEventHandler.RaiseCallbackEvent(string str)

{

this.callbackResult = str;

}

string ICallbackEventHandler.GetCallbackResult()

{

int categoryID = Convert.ToInt32(callbackResult);

BindToProduct(categoryID);

callbackResult = RenderElement(this.ddlProduct);

return callbackResult;

}

}

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