主题：求教蛇形输出该如何写代码

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Dim dt As DataTable = DataTables("表A")
Dim i As Integer = 1
Dim flag As Boolean = True
For Each dr As DataRow In dt.Select("", "第二列 desc")
    output.show(Math.Abs(i) & " " & dr("第二列") & " " & dr("第一列"))
    If flag = True
        i += 1
    Else
        i -= 1
    End If
    If i = 5  Then
        flag = False
        i = 4
    ElseIf i = 0 Then
        flag = True
        i = 1
    end if
Next

谢谢色大师