How to particular validation don't call in mvc 4 razor

See more:

MVC4

Dear ...

I have don't call particular validation in my web Page.
My class file.

public partial class AssessmentReporttext
    {
        public int ID { get; set; }
        [Required(ErrorMessage = "Assessment is required")]
        public string Assessment { get; set; }
        [Required(ErrorMessage = "Codetype is required")]
        public string CodeType { get; set; }
        [Required(ErrorMessage = "Description is required")]
        public string Description { get; set; }
        [Required(ErrorMessage = "Score is required")]
        public string Score { get; set; }
        public Nullable<System.DateTime> CreateDate { get; set; }
        public Nullable<System.DateTime> ModifiedDate { get; set; }
    }

And From Code..
@using (Html.BeginForm())
{













}
========
If i am change some value select then fair validation otherwise not fair in validation.