CODEWITHSUNDEEP
c#winformsvalidation
Simon
Simon

Reputation: 8357

Is the ValidationResult class suitable when validating the state of an object?

I have a C# WinForms application where multiple objects in a collection need to be valid before functions can be called in each object.

I have done some research and there is a ValidationResult class. Is this class suitable for returning validation data about an object, such as some properties are null, or is there another specific class that should be used?

Upvotes: 0

Views: 9409

Answers (1)

QuantumHive
QuantumHive

Reputation: 5683

You can use the RequiredAttribute from the System.ComponentModel.DataAnnotations namespace. Put this attribute on top of a property to validate if it's not null like so:

using System.ComponentModel.DataAnnotations;
public class MyDto
{
    [Required]
    public SomeObject SomeProperty { get; set; }
}

Likewise you can use more validation attributes from this namespace.

You can also create your own validation attributes if you inherit from ValidationAttribute. For example a Validation attribute that validates every object inside a list, something like:

[AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false)]
    public class ValidateCollectionAttribute : ValidationAttribute
    {
        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var collection = value as IEnumerable;

            if (collection != null)
            {
                foreach (object element in collection)
                {
                    //do validation
                }
            }

            return ValidationResult.Success;
        }
    }

Next you can use the Validator class to validate your object. You need to create a ValidationContext where you put your instance into, like so:

var instance = new MyDto { SomeProperty = null }; //note that I'm setting the property to null, while the property has the Required attribute
var context = new ValidationContext(instance);
var validationResults = new List<ValidationResult>(); //this list will contain all validation results
Validator.TryValidateObject(instance, context, validationResults, validateAllProperties: true);
var errors = validationResults.Where(r => r != ValidationResult.Success); //filter out all successful results since we are only interested in errors
if (errors.Any())
{
    //do whatever you like to do
}

Since I've instantiated the MyDto object with null for it's property, the Validator will return a ValidationResult that's been triggered by the Required attribute.

You could create a service that executes this kind of code, or you could just hard-wire this inside your code-behind. Whatever floats your boat.

Upvotes: 1

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