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我有 3 个下拉列表和一张图片。首先 ddl (Stamps: BMW, AUDI, VAZ) 从 SQL Server 获取他的数据并设置selectedIndex = 0. 第二个 ddl（型号：A6、TT、Z4、X5 等）取决于第一个 ddl。如果用户index = 0在第一个 ddl 中选择 (AUDI)，则第二个 ddl 显示 A6 和 TT。第三个 ddl（颜色）取决于第二个 ddl。如果第一个 ddl 中的用户select index = 0(AUDI) 和select index = 1第二个 ddl 中的 (TT)，则第三个 ddl 显示蓝色和银色。图像取决于所有三个 ddl。如何实现？

我的代码：

命名空间 DynamicWebApplication { 公共部分类 RentForm : System.Web.UI.Page { 公共静态布尔标志 = false; IBLClient 前端 = 新前端（）；

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            StampOfCarsDropDownList.DataSource = SqlDataSource1;
            StampOfCarsDropDownList.DataValueField = "Stamp";
            StampOfCarsDropDownList.DataTextField = "Stamp";
            StampOfCarsDropDownList.DataBind();

            if (StampOfCarsDropDownList.SelectedIndex == -1)
            {
                StampOfCarsDropDownList.SelectedIndex = 0;
                ModelOfCarsDropDownList.SelectedIndex = 0;
                ColorOfCarsDropDownList.SelectedIndex = 0;
            }

            ListItem stampOfCar = StampOfCarsDropDownList.Items[StampOfCarsDropDownList.SelectedIndex];
            string stamp = stampOfCar.Text;
            foreach (RentCar c in frontEnd.GetListOfModels(stamp))
            {
                ListItem temp = new ListItem(c.Model);
                if (!ModelOfCarsDropDownList.Items.Contains(temp))
                    ModelOfCarsDropDownList.Items.Add(temp);
            }

            ListItem modelOfCar = ModelOfCarsDropDownList.Items[ModelOfCarsDropDownList.SelectedIndex];
            string model = modelOfCar.Text;
            foreach (RentCar c in frontEnd.GetListOfModels(stamp))
            {
                ListItem temp = new ListItem(c.Color);
                if ((c.Model == model) && (!ColorOfCarsDropDownList.Items.Contains(temp)))
                    ColorOfCarsDropDownList.Items.Add(temp);
            }

            //UploadImage(stamp, model, ColorOfCarsDropDownList.Items[ColorOfCarsDropDownList.SelectedIndex].Text);
        }
    }

    protected void ColorOfCarsDropDownList_SelectedIndexChanged(object sender, EventArgs e)
    {
        ListItem stampOfCar = StampOfCarsDropDownList.Items[StampOfCarsDropDownList.SelectedIndex];
        string stamp = stampOfCar.Text;
        ListItem modelOfCar = ModelOfCarsDropDownList.Items[ModelOfCarsDropDownList.SelectedIndex];
        string model = modelOfCar.Text;
        ListItem colorOfCar = ColorOfCarsDropDownList.Items[ColorOfCarsDropDownList.SelectedIndex];
        string color = colorOfCar.Text;

        //UploadImage(stamp, model, color);
    }

    protected void ModelOfCarsDropDownList_SelectedIndexChanged(object sender, EventArgs e)
    {
        ColorOfCarsDropDownList.Items.Clear();
        ColorOfCarsDropDownList.SelectedIndex = 0;
        ListItem stampOfCar = StampOfCarsDropDownList.Items[StampOfCarsDropDownList.SelectedIndex];
        string stamp = stampOfCar.Text;
        ListItem modelOfCar = ModelOfCarsDropDownList.Items[ModelOfCarsDropDownList.SelectedIndex];
        string model = modelOfCar.Text;

        foreach (RentCar c in frontEnd.GetListOfModels(stamp))
        {
            ListItem temp = new ListItem(c.Color);
            if (c.Model == model)
                ColorOfCarsDropDownList.Items.Add(temp);
        }

        //UploadImage(stamp, model, ColorOfCarsDropDownList.Items[ColorOfCarsDropDownList.SelectedIndex].Text);
    }

    protected void StampOfCarsDropDownList_SelectedIndexChanged(object sender, EventArgs e)
    {
        ModelOfCarsDropDownList.Items.Clear();
        ModelOfCarsDropDownList.SelectedIndex = 0;
        ColorOfCarsDropDownList.Items.Clear();
        ColorOfCarsDropDownList.SelectedIndex = 0;

        ListItem stampOfCar = StampOfCarsDropDownList.Items[StampOfCarsDropDownList.SelectedIndex];
        string stamp = stampOfCar.Text;
        foreach (RentCar c in frontEnd.GetListOfModels(stamp))
        {
            ListItem temp = new ListItem(c.Model);
            if (!ModelOfCarsDropDownList.Items.Contains(temp))
                ModelOfCarsDropDownList.Items.Add(temp);
        }

        ListItem modelOfCar = ModelOfCarsDropDownList.Items[ModelOfCarsDropDownList.SelectedIndex];
        string model = modelOfCar.Text;
        foreach (RentCar c in frontEnd.GetListOfModels(stamp))
        {
            ListItem temp = new ListItem(c.Color);
            if (c.Model == model)
                ColorOfCarsDropDownList.Items.Add(temp);
        }

    //    UploadImage(stamp, model, ColorOfCarsDropDownList.Items[ColorOfCarsDropDownList.SelectedIndex].Text);
    }

    //protected void UploadImage(string stamp, string model, string color)
    //{
    //    byte[] fileBytes;
    //    foreach (RentCar c in frontEnd.GetListOfModels(stamp))
    //    {
    //        if ((c.Model == model) && (c.Stamp == stamp) && (c.Color == color))
    //        {
    //            fileBytes = (byte[])c.CarImage.ToArray();
    //            Stream msIn = new MemoryStream(fileBytes);
    //            msIn.Write(fileBytes, 0, fileBytes.Length);
    //            System.Drawing.Image im = System.Drawing.Image.FromStream(msIn);
    //            im.Save("C:/Users/Nickolay/Documents/Visual Studio 2010/Projects/RentCars/DynamicWebApplication/DBImages/CarImage" + c.Stamp + c.Model + c.Color + ".jpeg");
    //            carImage.ImageUrl = "DBImages/CarImage" + c.Stamp + c.Model + c.Color + ".jpeg";
    //        }
    //    }
    //}

}

}

我不明白这里有什么问题。我使用了 AutoPostBack。如果我从 ddl 中选择项目，我会得到空的 ddls。

对不起我的问题。我找到了解决我的问题的方法。这是小事。I forgot to set EnableViewState="true" in Master Page :( Therefore I got empty ddls when selected items (ddls not fire events)

4

3 回答 3

1

您必须使用控件的AutoPostBack和OnSelectedIndexChanged属性DropDownList。

一个例子

标记

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="default.aspx.cs" Inherits="Test.Default" %>
<!DOCTYPE html>
<html>
    <head runat="server">
        <title>Test</title>
    </head>
    <body>
        <form runat="server">
            <h1>Test</h1>
            <asp:DropDownList ID="First"
                              AutoPostBack="true"
                              DataTextField="FieldA"
                              DataValueField="FieldB"
                              OnSelectedIndexChanged="First_SelectedIndexChanged"
                              runat="server" />
            <asp:DropDownList ID="Second"
                              AutoPostBack="true"
                              DataTextField="FieldA"
                              DataValueField="FieldB"
                              OnSelectedIndexChanged="Second_SelectedIndexChanged"
                              runat="server" />
        </form>
    </body>
</html>

背后的代码

namespace Test
{
    using System;
    using System.Web.UI;
    using System.Web.UI.WebControls;

    public partial class Default : Page
    {
        protected void Page_Load(Object sender, EventArgs e)
        {
            if (!this.IsPostBack)
            {
                this.First.DataSource = null;

                this.First.DataBind();
            }
        }

        protected void First_SelectedIndexChanged(Object sender, EventArgs e)
        {
            String selectedValue = (sender as DropDownList).SelectedValue;

            // Use dataValue when getting the data for the second drop down.
            this.Second.DataSource = null;

            this.Second.DataBind();
        }

        protected void Second_SelectedIndexChanged(Object sender, EventArgs e)
        {
            // Do things here.
        }
    }
}
于 2011-06-24T12:09:19.540 回答
0

作为一个想法：

将这些 ddls 放入 UpdatePanel 并将 AutoPostBack 设置为 true。然后在两个第一个 ddl 中的每一个的 OnChange 事件处理程序中清除以下项目集合。

在 OnPreRender 事件中填充 ddl 中的项目 - 但仅当列表为空时 - 并使要填充的内容与前一个 ddl 的选定项目相对应。

于 2011-06-24T12:03:26.557 回答
0

你想要的只是级联下拉列表。您可以使用具有级联下拉列表控件的 Ajax 控件工具包，也可以使用下拉列表的 Selected 索引更改事件来实现您想要的，看看这篇文章它提供了所有代码。

于 2011-06-24T12:10:49.997 回答