vb.net中 listbox 有关问题

vb.net中 listbox 问题
vb.net中   listbox控件   数据通过数据库绑定   显示多条记录  
设为多选后   在界面上选择两条以上记录时   后台怎样能够取得所选记录的值
为什么我取得总是system........之类的


------解决方案--------------------
Dim Conn As OleDbConnection
Dim Cmd As OleDbCommand
Dim Rd As OleDbDataReader
Dim SQL As String
Dim Adpt As OleDbDataAdapter
Dim Ds As DataSet
Dim Provider = "Provider=Microsoft.Jet.OLEDB.4.0 "
Dim Database = "Data Source= " & Application.StartupPath() & "\db1.mdb "

Conn = New OleDbConnection(Provider & "; " & Database)
Conn.Open() '打开数据库
SQL = "Select * From one "
Cmd = New OleDbCommand(SQL, Conn)
Rd = Cmd.ExecuteReader()
While Rd.Read()
ListBox1.Items.Add(Rd.Item( "a "))
End While
Rd.Close()
Conn.Close()