主题：请问“统计筛选”示例中，假如在筛选树中的“产品”层级下再增加“客户”层级的统计，其结果只返回一行，统计数不对，请教代码如何写？

 代码

'首先生成统计表
Dim dt As DataTable
Dim b As New GroupTableBuilder("统计表1",DataTables("订单"))
b.Groups.AddDef("日期",DateGroupEnum.Year,"年")
b.Groups.AddDef("日期",DateGroupEnum.Month,"月")
b.Groups.AddDef("产品")
b.Groups.AddDef("客户")
b.Totals.AddDef("客户",AggregateEnum.Count,"订单数") '根据客户列来统计记录数,也就是订单数
dt = b.Build(False) '参数设置为False,生成一个临时表,不在主界面显示
'然后根据统计表生成目录树
Dim trv As WinForm.TreeView = e.Form.Controls("TreeView1")
trv.BuildTree(dt, "年|月|产品|客户")
trv.StopRedraw
For Each nd As WinForm.TreeNode In trv.AllNodes
    Dim Year As Integer = nd.DataRow("年")
    Dim Month As Integer = nd.DataRow("月")
    Dim Product As String = nd.DataRow("产品")
    Select Case nd.Level
        Case 0
            nd.Text = nd.text & "年(" & dt.Compute("Sum(订单数)","年 = " & Year) & "条)"
        Case 1
            nd.Text = nd.text & "月(" & dt.Compute("Sum(订单数)","年 = " & Year & " And 月 = " & Month) & "条)"
        Case 2
            nd.Text = nd.text & "月(" & dt.Compute("Sum(订单数)","年 = " & Year & " And 月 = " & Month & " and 产品 = '" & Product  & "'") & "条)"
        Case 3
            nd.Text = nd.text & "(" & nd.DataRow("订单数") & "条)"
    End Select
Next
trv.Nodes.Insert("显示所有行","显示所有行(" & dt.Compute("Sum(订单数)") & "条)",0)
trv.ResumeRedraw