主题：[求助]日期列设置目录树的问题

Dim cmd1 As New SQLCommand
Dim dt1 As DataTable
cmd1.CommandText = "SELECT DISTINCT 日期,单号 From {入库}"
dt1 = cmd1.ExecuteReader()
Dim trv1 As WinForm.TreeView = e.Form.Controls("TreeView2")
trv1.BuildDataTree(dt1, "","日期","单号")
trv1.Nodes.Insert("全部单据",0)

这段代码生成的目录树，日期显示为2012-01-01-00:00:00我需要的是2012-01-01该怎样实现

请大家帮忙看看我错在哪里，谢谢！