1. The HTML Markup
<div>
<asp:ListBox ID="ListBox1" runat="server"></asp:ListBox>  <br />
<asp:Button ID="Button1" runat="server" Text="Get Selected Values" OnClick="Button1_Click" />
</div>
　　2. The button event
protected void Page_Load(object sender， EventArgs e)
{
if (!IsPostBack)
{
//填充数据
DataTable dt = new DataTable();
dt.Columns.Add(new DataColumn() { ColumnName = "Id"， DataType = typeof(int) });
dt.Columns.Add(new DataColumn() { ColumnName = "Name"， DataType = typeof(string) });
dt.Rows.Add(1， "Scott");
dt.Rows.Add(2， "John");
dt.Rows.Add(3， "Tom");
dt.Rows.Add(4， "Ross");
ListBox1.DataValueField = "Id";
ListBox1.DataTextField = "Name";
ListBox1.DataSource = dt;
ListBox1.DataBind();
}
}
protected void Button1_Click(object sender， EventArgs e)
{
int id = int.Parse(ListBox1.SelectedItem.Value);
Response.Write(id);
}