The System.ComponentModel.DataAnnotations.ValidationResult class was created for RIA Services, and it was introduced in Silverlight 3.0 and then added into .NET 4.0. A ValidationResult represents a validation error condition, specifying the error message and, optionally, any member names that the error corresponds to. If you use the [Required] attribute, the [Range] attribute, [StringLength], or any of the other provided ValidationAttribute classes, then ValidationResult instances are created to represent any validation failures. If you have used the [CustomValidation] attribute or if you have derived from ValidationAttribute yourself, you have likely returned an instance of ValidationResult in your code, or ValidationResult.Success if validation...