遇到问题，控件ListItem和DropDownList绑定数据库数据后selectedindex数
> 值始终为-1,导致无法选定索引号。
> 考虑解决办法：不直接绑定，数据库数据连接到ArrayList后再用控件的
> Items.Add方法添加内容
Dim myConn As SqlConnection = New SqlConnection("Server=localhost;" & _
"Database=Pubs;UID=sa;PWD=")
Dim myCmd As SqlCommand = New SqlCommand("SELECT au_id," & _
"au_lname FROM Authors", myConn)
myConn.Open()
Dim myReader As SqlDataReader = myCmd.ExecuteReader()
'Set up the data binding.
AuthorList.DataSource = myReader
AuthorList.DataTextField = "au_lname"
AuthorList.DataValueField = "au_id"
AuthorList.DataBind()
'Close the connection.
myConn.Close()
myReader.Close()
'Add the item at the first position.
AuthorList.Items.Insert(0, "<-- Select -->")
