主题：求助:死循环了

提示是'编码表'无效

Dim tb As Table = args(0) '要操作的表
Dim dr As DataRow
Dim cmd1 As new SQLCommand
Dim cmd2 As New SQLCommand
Dim Key As Integer
cmd1.C
cmd2.C
cmd1.CommandText = "Select Count(*) From {编码表} Where [表名] = '" & tb.Name & "'"
cmd1.commandText = "Select [顺序号] From {编码表} Where [表名]='" & tb.Name & "'"
Do
   
    Key = cmd1.ExecuteScalar() '从后台获得顺序号
    cmd2.commandText = "Update {编码表} Set [顺序号] = " & (Key + 1) & " Where [表名] = '" & tb.Name & "'"
    If cmd2.ExecuteNonQuery() > 0 Then '更新顺序号
        Exit Do '更新成功则退出循环
    End If
Loop
Dim d As Boolean
cmd1.CommandText =  "Select [日期] From {编码表} Where [表名]='" & tb.Name & "'"
d = cmd1.ExecuteScalar
If d = 0
'________________前缀提取_______________
cmd1.commandText = "Select [前缀] From {编码表} Where [表名]='" & tb.Name & "'"
Return cmd1.ExecuteScalar() & Format(Key,"0000")
Else
cmd1.commandText = "Select [前缀] From {编码表} Where [表名]='" & tb.Name & "'"
Return cmd1.ExecuteScalar() & Format(Date.Today,"yyyyMMdd") & Format(Key,"0000")
End If