1. selectedIndex——指的是dropdownlist中选项的索引，为int，从0开始，可读可写
2. selectedItem——指的是选中的dropdownlist中选项，为ListItem，只读不写
3. selectedValue——指的是选中的dropdownlist中选项的值，为string， 只读不写
4. selectedItem.Text——指的是选中的dropdownlist中选项的文本内容，与selectedItems的值一样为string，可读可写
5. selectedItem.value——指的是选中的dropdownlist中选项的值，与selectedValue的值一样，为string，可读可写
光看文字可能不太理解，我也是通过程序来加深理解的，下面举个例子：.
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="dropdown.aspx.cs" Inherits="dropdown" %>
<!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>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:DropDownList ID="DropDownList1" runat="server">
<asp:ListItem Value="1">北京</asp:ListItem>
<asp:ListItem Value="2">上海</asp:ListItem>
<asp:ListItem Value="3">广州</asp:ListItem>
</asp:DropDownList>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="check" /><br />
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
<br />
<asp:Label ID="Label2" runat="server" Text=""></asp:Label>
<br />
<asp:Label ID="Label3" runat="server" Text=""></asp:Label><br />
<asp:Label ID="Label4" runat="server" Text=""></asp:Label>
<br />
<asp:Label ID="Label5" runat="server" Text=""></asp:Label>
</div>
</form>
</body>
</html>
后台代码
using System;
using System.Data;
using System.Configuration;
using System.Collections;
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 dropdown : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Button1_Click(object sender, EventArgs e)
{
Label1.Text = "selectedIndex=" + DropDownList1.SelectedIndex;
Label2.Text = "selectedItem=" + DropDownList1.SelectedItem;
Label3.Text = "selectedValue=" + DropDownList1.SelectedValue;
Label4.Text = "selectedItem.text=" + DropDownList1.SelectedItem.Text;
Label5.Text = "selectedItem.value=" + DropDownList1.SelectedItem.Value;
}
}
