主题：求编号的自动生成代码

要达到"实话实说”的编号要求，我也实话实说，还真有点费劲，参考了狐狸他爹的流水账编码（狐狸他爹的高效率流水账那可真叫一个绝），勉强完成，经测试，符合“实话实说”的要求

Dim d As Date = e.DataRow("日期")
Dim StartDate As Date
Dim EndDate As Date
Dim Month As Integer  = d.Month
Dim Year As Integer = d.Year
StartDate = New Date(Year,Month,1)
EndDate = New Date(Year,Month,Date.DaysInMonth(Year,Month))
If e.DataCol.Name = "日期" Then
    If e.DataRow.IsNull("日期") Then
        e.DataRow("编号") = Nothing
    Else
        If e.NewValue <> Nothing And e.DataRow("编号") = Nothing Then
            'e.DataRow("编号") ="AA" & format(e.NewValue,"yyMMdd")    '可替换
            e.DataRow("编号") ="AA" & CStr(e.NewValue).Remove(0,2).Remove(2,1).Remove(4,1)
            Dim dr As DataRow
            Dim mr As DataRow = e.DataRow
            Dim drs As List(of DataRow)
            dr = e.DataTable.Find("[_SortKey] < " & mr("_SortKey") & "  And [日期] = #" & d & "#", "[_SortKey] Desc")
            If dr Is Nothing Then
                mr("编号") = mr("编号") & format(1,"000")
                dr = mr
            End If
            drs = e.DataTable.Select("[_SortKey] >= " & dr("_SortKey") & " And [日期] = '" & d & "'", "[_SortKey]")
            For i As Integer = 1 To drs.Count - 1
                drs(i)("编号") ="AA" & drs(i-1)("编号").SubString(drs(i-1)("编号").Length - 9) + 1
            Next
        End If
    End If
End If

说明：如果要求编号确立后不允许修改的，将[_SortKey] 替换为[_Identify]

如果要达到上面的代码,一句就可以了:

If e.DataCol.Name = "日期" Then
    e.DataRow("编号")  = "AA"& Format(e.DataRow("日期"),"yyMMdd") & Format(e.DataTable.Compute("count(日期)", "[日期] = #" & e.DataRow("日期")  & "# And [_identify] < 50" & e.DataRow("_Identify")),"0000")
End If

如果是这个效果:

If e.DataCol.Name = "日期" Then
    If e.DataRow.IsNull("日期") Then
        e.DataRow("编号") = Nothing
    Else
        If e.NewValue <> Nothing And e.DataRow("编号") = Nothing Then
            Dim s As String ="AA" & format(e.DataRow("日期"),"yyMMdd")    '只修改了这个地方···
            Dim i1 As String = e.DataTable.Compute("Max(第三列)", "[日期] = #" & e.DataRow("日期")  & "#" )
            Dim n As Integer
            If s = left(i1,8) Then
                n=CInt(right(i1,3))
            Else
                n=0
            End If
            s= s & format(n+1,"000")
            e.DataRow("第三列")=s
        End If
    End If
End If