主题：关于SQL新增行的问题

Dim cmd As new SQLCommand
Dim dt As DataTable
cmd.C

cmd.commandtext = " select [_Identify] form {客户汇总} where [_Identify] is null "

dt = cmd.ExecuteReader(True) '记得将参数设置为True
Dim dr As DataRow = dt.AddNew
dr.save
Output.show(dr("_Identify"))

为什么结果是：0 。要怎么才能得到 [_Identify] 的值？多谢！