如何在ASP.NET中验证日历控件

Question

I'm using Asp.net and c# as my back end and I want to validate my check_in and check_out date in such a way that it the check_in is not before check_out and also check_in and check_out calendar controls cannot be blank, thanks.

.aspx page

<asp:Calendar ID="checkin" runat="server"></asp:Calendar>

<asp:Calendar ID="checkout" runat="server"></asp:Calendar>

Answer 1

            if (checkin.SelectedDate > checkout.SelectedDate)
            {
               // Not Valid
            }