1、DropDownList控件
<asp:DropDownList runat="server" ID="DropDownList1" AutoPostBack="true" OnSelectedIndexChanged="DropDownList_SelectedIndexChanged"></asp:DropDownList>
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ArrayList color = new ArrayList();
color.Add("Red");
color.Add("Green");
color.Add("Blue");
color.Add("LightGray");
DropDownList1.DataSource = color;
DropDownList1.DataBind();
}
}
protected void DropDownList_SelectedIndexChanged(object sender, EventArgs e)
{
string color = this.DropDownList1.SelectedItem.Value;
switch (color)
{
case "Red":
this.DropDownList1.BackColor = System.Drawing.Color.Red;
break;
case "Green":
this.DropDownList1.BackColor = System.Drawing.Color.Green;
break;
case "Blue":
this.DropDownList1.BackColor = System.Drawing.Color.Blue;
break;
case "LightGray":
this.DropDownList1.BackColor = System.Drawing.Color.LightGray;
break;
default:
this.DropDownList1.BackColor = System.Drawing.Color.White;
break;
}
}
}
（1）获取DropDownList控件选项的索引号和标题
int Index = DropDownList1.SelectedIndex;//获取选项的索引号
int Index = DropDownList1.SelectedItem;//获取选项的标题
（2）向 DropDownList控件的下拉列表框中添加列表项
DropDownList1.Items.Add(new ListItem(“ASP.NET”,”0″));
DropDownList1.Items.Add(new ListItem(“VB.NET”,”1″));
DropDownList1.Items.Add(new ListItem(“C#.NET”,”2″));
DropDownList1.Items.Add(new ListItem(“VB”,”3″));
（3）删除选项的DropDownList控件的列表项
ListItem Item = DropDownList1.SelectedItem;
DropDownList1.Items.Remove(Item);
（4）清除所有DropDownList控件的列表项
DropDownList1.Items.Clear();
（5）获取DropDownList控件包含的列表项数
int count = DropDownList1.Items.Count;