日历挂件时间先后的验证 (适用于格式2015-08-12)
开始时间
<asp:TextBox ID="txt_lsstart" runat="server" validate="isRequired" onfocus="WdatePicker({maxDate:'#F{$dp.$D(\'txt_lsend\')}', dateFmt:'yyyy-MM-dd'})"></asp:TextBox>
结束时间
<asp:TextBox ID="txt_lsend" runat="server" validate="isRequired" onfocus="WdatePicker({minDate:'#F{$dp.$D(\'txt_lsstart\')}', dateFmt:'yyyy-MM-dd'})"></asp:TextBox>