日期时间验证错误

Question

我没有在表单提交时收到验证错误，而是显示控制器设置的通用错误页面。

控制器：

   public ActionResult Add(Loan loan)
        {
            try
            {
                    _dbLoan.Loans.Add(loan);
                    _dbLoan.SaveChanges();
                    return RedirectToAction("Index");
            }

            catch
            {
                return View("Error");
            }
        }

部分视图：

<div class="form-group input-group-sm">
    @Html.LabelFor(model => model.DeliveryDate)
    @Html.TextBoxFor(model => model.DeliveryDate, new { @class = "form-control datepicker", placeholder = "Enter Delivery date here  DD-MM-YYYY..." })
    @Html.ValidationMessageFor(model => model.DeliveryDate)
</div>

型号：

public class Loan : IValidatableObject
{

    /// <summary>
    /// Instance Variables
    /// </summary>
    [Key]
    public int LoanID { get; set; }


    [Display(Name = "Select Date")]
    [Required]
    [DataType(DataType.Date)]
    public DateTime DeliveryDate { get; set; }

    IEnumerable<ValidationResult> IValidatableObject.Validate(ValidationContext validationContext)
    {
        List<ValidationResult> res = new List<ValidationResult>();
        if (DeliveryDate < DateTime.Today)
        {
            ValidationResult mss = new ValidationResult("Appointment date must not be in the past. Please try again.");
            res.Add(mss);

        }
        return res;
    }

任何人都可以帮助解决为什么忽略验证错误？ 感谢。