Data Annotation Validation in ASP.NET MVC

http://www.asp.net/mvc/tutorials/older-versions/models-(data)/validation-with-the-data-annotation-validators-cs

 public class Product
    {
        public int Id { get; set; }

        [Required]
        [StringLength(10)]
        public string Name { get; set; }

        [Required]
        public string Description { get; set; }

        [DisplayName("Price")]
        [Required]
        [RegularExpression(@"^\$?\d+(\.(\d{2}))?$")]
        public decimal UnitPrice { get; set; }
    }