requiredif entity framework empty field

Question

I am validating a field based on another field using custom validation in MVC and I came across this implementation:

 public class RequiredIfAttribute : ValidationAttribute
    {
        private String PropertyName { get; set; }
        private String ErrorMessage { get; set; }
        private Object DesiredValue { get; set; }

        public RequiredIfAttribute(String propertyName, Object desiredvalue, String errormessage)
        {
            this.PropertyName = propertyName;
            this.DesiredValue = desiredvalue;
            this.ErrorMessage = errormessage;
        }

        protected override ValidationResult IsValid(object value, ValidationContext context)
        {
            Object instance = context.ObjectInstance;
            Type type = instance.GetType();
            Object proprtyvalue = type.GetProperty(PropertyName).GetValue(instance, null);
            if (proprtyvalue.ToString() == DesiredValue.ToString())
            {
                return new ValidationResult(ErrorMessage);
            }
            return ValidationResult.Success;
        }
    }

And I have a simple class defined as follows:

public class Person
{
    public int PersonID { get; set; }
    public string name { set; get; }
    [RequiredIf("name","","Address is required")]
    public string addr { get; set; }
}

When I run the page, I get a Object reference not set to an instance of an object. error but changing the line to [RequiredIf("name","John","Address is required")] yields expected results. My question is, how do you use it to check if the field is empty.

I have also tried changing the line to [RequiredIf("name",null,"Address is required")] but I get the same error.

mpora · Accepted Answer · 2013-02-22 21:38:54Z

2

This seems to work:

protected override ValidationResult IsValid(object value, ValidationContext context)
        {
            if (value != null) { return ValidationResult.Success; }

            Object instance = context.ObjectInstance;
            Type type = instance.GetType();
            Object proprtyvalue = type.GetProperty(PropertyName).GetValue(instance, null);
            if (proprtyvalue == null) {
               return new ValidationResult(ErrorMessage);
            }
            return ValidationResult.Success;
        }

answered Feb 22, 2013 at 21:38

mpora

1,4895 gold badges26 silver badges67 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

AroglDarthu · Accepted Answer · 2013-02-22 20:12:59Z

0

You did not post the actual Person instantiations that you're testing, so I'm just guessing: make sure that proprtyvalue of PropertyName is not null before trying to call ToString() on it. So your Person.Name cannot be null!

answered Feb 22, 2013 at 20:12

AroglDarthu

1,18110 silver badges19 bronze badges

Collectives™ on Stack Overflow

requiredif entity framework empty field

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related