主题：对于外部数据表的统计

Dim doc As New PrintDoc
Dim rt As New prt.RenderTable
Dim cmd As New SQLCommand '定义一个SQL命令
Dim dt As DataTable '定义一个数据表变量
Dim Count As Integer = 0
cmd.CommandText = "Select 产品,Count(日期) As 订单数,Sum(数量) As 数量,Sum(金额) As 金额 From {订单} Group By 产品"
dt = cmd.ExecuteReader() '生成一个临时表
For Each Col AS DataCol In Dt.DataCols
    rt.Cells(0,Count).Text = Col.Name
    For r As integer = 0 To dt.DataRows.Count - 1
        rt.Cells(r +1,Count).Text = dt.DataRows(r)(Col.Name)
    Next
    Count = Count + 1
Next
rt.Style.Gridlines.All = New prt.Linedef(Color.Gray) '灰色网格线
rt.CellStyle.Spacing.All = 1 '内容距离网格线1毫米
rt.Rows(0).Style.TextAlignHorz = prt.AlignHorzEnum.Center '第一行内容水平居中
doc.Body.Children.Add(rt)
doc.Preview()

以上代码是否适用于外部数据表啊，我执行时，提示未将对象引用到实例。。。