[Display(Order = 0)]
[Required(ErrorMessage = "Please provide a name")]
public string Name { get; set; }
[Range(0, 999)]
public Nullable<decimal> Price { get; set; }
[RegularExpression(@"^http\://[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(/\S*)?$",
                    ErrorMessage = "Please use standard Url format")]
public string Uri { get; set; }

[CustomValidation(typeof(PlateValidationRules),
                  "IsDescriptionValid")]
public string Description { get; set; }

1:         public static ValidationResult IsDescriptionValid(string description)
2:         {
3:             if (description != null && description.Split().Length < 5)
4:             {
5:                 var vr = new ValidationResult("Valid descriptions must have 5 or more words.",
6:                     new string[] { "Description" });
7:                 return vr;
8:             }
9: 
10:             return ValidationResult.Success;
11:         }
12: 

<riaControls:DomainDataSource  SubmittedChanges="plateDomainDataSource_SubmittedChanges"
 
        private void plateDomainDataSource_SubmittedChanges(object sender, SubmittedChangesEventArgs e)
        {
            if (e.HasError &&
                e.EntitiesInError.All(t => t.HasValidationErrors))
            {
                e.MarkErrorAsHandled();
            }
            else
            {
                System.Windows.MessageBox.Show(e.Error.ToString(), "Load Error", System.Windows.MessageBoxButton.OK);
                e.MarkErrorAsHandled();
            }
        }