编号列改成字符列，DataRowAdded事件代码

Dim d As Date = Date.Today
Dim y As Integer = d.Year
Dim m As Integer = d.Month
Dim Days As Integer = Date.DaysInMonth(y,m)
Dim fd As Date = New Date(y,m,1) \'获得该月的第一天
Dim ld As Date = New Date(y,m,Days) \'获得该月的最后一天
Dim bh As String = Format(d,"POyyyyMM-") \'生成编号的前6位,4位年,2位月.
Dim max As String
Dim idx As Integer
max = e.DataTable.Compute("Max(订单编号)","订单编号 like \'" & bh & "%\' and [_Identify] <> " & e.DataRow("_Identify")) \'取得该月的最大编号
If max > "" Then \'如果存在最大编号
    idx = CInt(max.Substring(bh.length,3)) + 1 \'获得最大编号的后三位顺序号,并加1
Else
    idx = 1 \'否则顺序号等于1
End If
e.DataRow("订单编号") = bh & Format(idx,"000")