C# 从另一个listbox.net asp打开新的listbox

我对asp.net开发和c#非常陌生。我已经创建了两个列表框并命名它们。我的第一个列表框将包含许多列表项。我希望当我按下列表框上的一个项目时，我的另一个列表框将加载一些特定的项目。假设我的第一个列表框包含许多汽车。当我点击一辆车时，我的另一个列表框将显示我选择的那辆车的所有部件。我感谢所有我能得到的帮助。

假设此示例适用于类别和项目（与汽车和部件相同）

我创建了一个winform，其中包含两个列表框listbox1和listbox2，这就是我的Form1.cs的外观：

namespace WinFormsApp
{
    public partial class Form1 : Form
    {
        private List<Category> categories;

        public Form1()
        {
            InitializeComponent();

            categories = new List<Category>();

            var categoryOne = new Category { Name = "Category 1"} ;
            categoryOne.Items.Add( new CategoryItem { Name = "Item 1"} );

            var categoryTwo = new Category { Name = "Category 2" };
            categoryTwo.Items.Add( new CategoryItem { Name = "Item 2" } );

            categories.Add( categoryOne );
            categories.Add( categoryTwo );
        }

        private void Form1_Load(object sender, System.EventArgs e)
        {
            categoryBindingSource.DataSource = categories;
        }
    }

    public class Category
    {
        public string Name { get; set; }

        public List<CategoryItem> Items { get; private set; }

        public Category()
        {
            Items = new List<CategoryItem>();
        }
    }

    public class CategoryItem
    {
        public string Name { get; set; }
    }
}

---

这是一个非常广泛的问题。 但是，这里有一些东西可以让你开始

标记：

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeBehind="Default.aspx.cs" Inherits="WebApplication1._Default" %>

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
    <p>
        <asp:ListBox runat="server" id="lbCars" OnSelectedIndexChanged="lbCars_SelectedIndexChanged" Width="200px" Height="100px" AutoPostBack="true"></asp:ListBox>
    </p>
    <p>
        <asp:ListBox runat="server" id="lbParts"  Width="200px" Height="100px"></asp:ListBox>
    </p> 
</asp:Content>

---

使用ListBox.SelectedIndexChanged EventTag作为ASP.NET，如果这是您在他的第一句话中使用的，OP说：“我对ASP.NET开发和c#非常陌生。”winforms示例不错，但…：）非常感谢。但是我在LineLoadPartsList（this.lbCars.SelectedValue）上得到一个NullPointerExection；我找不到错误，有什么提示吗？看起来像是

lbCars。SelectedValue

是

null

。如果（！string.IsNullOrEmpty（lbCars.SelectedValues））在

LoadPartsList（this.lbCars.SelectedValues）之前添加

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeBehind="Default.aspx.cs" Inherits="WebApplication1._Default" %>

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
    <p>
        <asp:ListBox runat="server" id="lbCars" OnSelectedIndexChanged="lbCars_SelectedIndexChanged" Width="200px" Height="100px" AutoPostBack="true"></asp:ListBox>
    </p>
    <p>
        <asp:ListBox runat="server" id="lbParts"  Width="200px" Height="100px"></asp:ListBox>
    </p> 
</asp:Content>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication1
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                LoadCarsList();

            }
        }


        protected void lbCars_SelectedIndexChanged(object sender, EventArgs e)
        {   
            //this will be executed when selected item in list of cars is changes
            //load parts
            LoadPartsList(this.lbCars.SelectedValue);
        }

        protected void LoadCarsList()
        {
            //here is the place to load cars list from database.
            //for this example, cars are hard-coded
            this.lbCars.Items.Clear();
            this.lbCars.Items.Add(new ListItem("Peugeot", "1"));
            this.lbCars.Items.Add(new ListItem("VW", "2"));
            this.lbCars.Items.Add(new ListItem("Ford", "3"));
            this.lbCars.Items.Add(new ListItem("Fiat", "4"));
        }

        protected void LoadPartsList(string carId)
        {
            //this will be called when you s
            this.lbParts.Items.Clear();

            this.lbParts.Items.Add("part one for car " + carId);
            this.lbParts.Items.Add("part two for car " + carId);
            this.lbParts.Items.Add("part three for car " + carId);

        }
    }
}