public partial class Dinner :EntityObject { 

for example title property 
 [EdmScalarPropertyAttribute(EntityKeyProperty=false, IsNullable=false)]
        [DataMemberAttribute()]
        public global::System.String Title
        {
            get
            {
                return _Title;
            }
            set
            {
                OnTitleChanging(value);
                ReportPropertyChanging("Title");
                _Title = StructuralObject.SetValidValue(value, false);// here throws Exception * 
                ReportPropertyChanged("Title");
                OnTitleChanged();
            }
        }
            
        }

[MetadataType(typeof(Dinner_Validation))]
    public partial class Dinner {
    }

    public class Dinner_Validation {
        [Required(ErrorMessage = "Title is required")]
        [StringLength(50, ErrorMessage = "Title may not be longer than 50 characters")]
        public string Title { get; set; }
        [Required(ErrorMessage = "Description is require")]
        [StringLength(265, ErrorMessage = "Description must be 256 characters or less")]
        public string Description { get; set; }
        [Required(ErrorMessage = "Address is required")]
        public string Address { get; set; }
        [Required(ErrorMessage = "Country is required")]
        public string Country { get; set; }
        [Required(ErrorMessage = "Phone# is required")]
        public string ContactPhone { get; set; }
        [Required(ErrorMessage = "EventDate is required")]
        public DateTime EventDate { get; set; }
        [Required(ErrorMessage = "HostedBy is required")]
        public string HostedBy { get; set; }
        [Required(ErrorMessage = "Latitude is required")]
        public double Latitude { get; set; }
        [Required(ErrorMessage = "Longitude is required")]
        public double Longitude { get; set; }
    }