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预览时的错误提示

以下是我的代码：我测试过，第一层for each正常，第二层出错，找一上午没不到原因，请帮我看一下，错在哪里，谢谢

Dim cmd As New SQLCommand
Dim dt As DataTable
cmd.C
cmd.CommandText = "SELECT * From {cd} where sjcdmc is null"
dt = cmd.ExecuteReader()

Dim cmd1 As New SQLCommand
Dim dt1 As DataTable
cmd1.C

For Each dr As DataRow In dt.DataRows
    tpb.pages.add(dr("cdmc"),dr("cdsm"),dr("cdtp")).Collapsed = True
    cmd1.CommandText = "SELECT * From {cd} where sjcdmc =\'" & dr("cdmc") & "\'"
    dt1 = cmd1.ExecuteReader()
    For Each dr1 As DataRow In dt1.DataRows
        tpb.Pages("cdmc").Links.Add(dr1("cdmc"), dr1("cdsm"))
    Next
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