Validating Properties with System.ComponentModel.DataAnnotations.Validator

Question

I have my Entity setup with Data Annotation validation attributes and i am trying to validate it using the static Validator class but i am getting different exceptions, isn't this the right way to do it:

string _ValidateProperty(object instance, string propertyName)
        {
            var validationContext = new ValidationContext(instance, null, null);
            validationContext.MemberName = propertyName;
            var validationResults = new List<ValidationResult>();
            var isValid = Validator.TryValidateProperty(instance, validationContext, validationResults);
            if (isValid)
                return string.Empty;
            return validationResults.FirstOrDefault<ValidationResult>().ErrorMessage;
        }

Answer 1

You havent stated what Exception you are receiving but it appears you are passing your instance to the TryValidateProperty method when you should be passing the value of the particular property.

Instead of

Validator.TryValidateProperty(instance, validationContext, validationResults);

try

Validator.TryValidateProperty(propertyValue, validationContext, validationResults);

you will have to pass propertyValue down to your method (or use reflection which will be slower)

eg

_ValidateProperty(someObject, "Field1", someObject.Field1);