VB2008将Listbox里的内容添加到Access新行中，高手请进！

Question

我想将listbox里一个值添加到数据库中新的一行去，以下是程序代码，但程序运行后老是说“未将对象引用设置到对象”，希望这里有懂的人能够帮忙看看这个问题，谢谢了！！                Dim OLDA As OleDbDataAdapter = New OleDbDataAdapter
                Dim conn As OleDbConnection = New OleDbConnection
                Dim cmd As OleDbCommand = New OleDbCommand
                Dim DT As DataTable = New DataTable
                Dim DataSet1 As DataSet = New DataSet
                conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\competition\files\food.mdb"
                cmd.CommandText = "select * from 食品流通表"
                cmd.Connection = conn
                OLDA.SelectCommand = cmd
                Dim builder As OleDb.OleDbCommandBuilder = New OleDbCommandBuilder(OLDA)
                conn.Open()
                OLDA.Fill(DataSet1, "食品流通表")
                DT = DataSet1.Tables("食品流通表")
                conn.Close()
                conn = Nothing
                Dim myrow As DataRow = DT.NewRow()
                myrow("ID") = ListBox1.Items.Item(0)
                DT.Rows.Add(myrow)
                conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\competition\files\food.mdb"
                cmd.CommandText = " INSERT into 食品流通表(ID) values  ( '" & ListBox1.Items(0) & "' )"
                cmd.Connection = conn
                OLDA.InsertCommand = cmd
                Dim builder1 As OleDb.OleDbCommandBuilder = New OleDb.OleDbCommandBuilder
                conn.Open()
                DataSet1 = New DataSet()
                OLDA.Fill(DataSet1, "食品流通表")
                conn.Close()
                conn = Nothing