累加编号时总是会卡在某个数上半天过不去符上程序段

VB.NET code

 Dim i As Integer

    Private Sub Button7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button7.Click
      
               Dim x As String
        connectionstring = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\pigsystem\pigsystem\zmsf.mdb"
        Dim querystring As String = "Select top 1 编号 from zzlr order by 编号 desc "
        Dim conn As New OleDb.OleDbConnection(connectionstring)
        Try
            conn.Open()
            Dim cmd As New OleDb.OleDbCommand(querystring, conn)
            Dim reader As OleDb.OleDbDataReader
            reader = cmd.ExecuteReader()
            reader.Read()
            i = reader("编号")
            i = i + 1
        Catch ex As Exception
        End Try
        x = CStr(i)
        TextBox23.Text = x
        connectionstring = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\pigsystem\pigsystem\zmsf.mdb"
        Dim querystring2 As String = "insert into zzlr(编号) values('" & x & "')"
        Dim conn2 As New OleDb.OleDbConnection(connectionstring)
        Try
            conn2.Open()
            Dim cmd2 As New OleDb.OleDbCommand(querystring2, conn2)
            cmd2.ExecuteNonQuery()
        Catch ex As Exception
        End Try
     End Sub

这段代码实现功能没有问题，点击Button7一次，表中插入一条新记录并且编号加1，并把编号反馈到TextBox23.Text中，只是在进行累加时，有时会卡到某个数上没有反应了，特别是点的很快时，比如到26，就停住了，没有反应了，点也不会再累加，这时如果退出再进程序，又会从26重新继续，或者如果不退出，狂点几下Button7也会跳过这个数就如同宕机一样。请高人指点看看是那个环节出了问题。

在一个过程中，数据库打开了两次吧？

可是我试过放在同一段程序里，打开一次数据库，却不能实现累加。

没有关闭连接。conn.close()；