在C#ASP.NET中使用dropdownlist
本文关键字：dropdownlist C#ASP NET | 更新日期: 2023-09-27 18:00:23
我有3个下拉列表和一个图像。第一个ddl（Stamps:BBMW，AUDI，VAZ）从SQL Server获取数据并设置selectedIndex = 0。第二个ddl（型号：A6、TT、Z4、X5等）取决于第一个ddl。如果用户在第一个ddl中选择index = 0（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）和第二个ddl的select index = 1（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{公共分部类RentForm:System.Web.UI.Page{public static bool flag=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";
// }
// }
//}
}
}
我不明白这里出了什么问题。我使用了AutoPostBack。如果我从ddl中选择项目，我会得到空的ddl。
对不起我的问题。我找到了解决问题的办法。这是一件小事。我忘记在母版页中设置EnableViewState="true"：（因此，当选择项目时，我得到了空的ddls（ddls不是激发事件）
您必须使用DropDownList控件的AutoPostBack和OnSelectedIndexChanged属性。
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.
}
}
}
作为一个想法：
将这些ddl放在UpdatePanel中，并将它们的AutoPostBack设置为true。然后，在前两个ddl的OnChange事件处理程序中，清除以下各项的items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上一个ddl的选定项目相对应。
您只需要级联Dropdownlists。您可以使用具有级联下拉列表控件的Ajax Control Toolkit，也可以使用下拉列表的Selected index change事件来实现您想要的内容，看看这篇文章，它提供了所有代码。