wrong comparison between textbox date and column date database (gets textbox always smaller than column date)

wrong comparison between textbox date and column date database (gets textbox always smaller than column date)
this my code
Txtddate.text have calender extender sourcecode :
<td class="style7"> <asp:TextBox ID="Txtddate" runat="server" CssClass="EDIT" ></asp:TextBox></td> <asp:CalendarExtender ID="CalendarExtender2" TargetControlID="Txtddate" PopupButtonID="Txtddate" Format="dd/MM/yyyy" runat="server"> </asp:CalendarExtender>
in events 
Try Dim op As New Payc Dim opr As New Pay Dim dt As DataTable = op.pipdued(ViewState("idpay")) opr.ddatep = Txtddate.Text If Txtddate.Text <> Nothing And Txtddate.Text > dt.Rows(0)("plin_duedate").ToString() Then ...