ASP.NET Core - Create custom model validation

Question

In previous versions of ASP.NET MVC the way to add custom validation to your model was by implementing the IValidatableObject and implementing your own Validate() method.

Here's what I have implemented:

public class BestModelEver: IValidatableObject 
{
    public DateTime? Birthday { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) 
    {
        if (Birthday.HasValue) 
        {
          yield return new ValidationResult("Error message goes here");
        }
    }
}

Is this still the recommended way of adding custom validation to a model in ASP.NET Core? Using IValidatableObject takes on a System.ComponentModel.DataAnnotations dependency.

Ian Kemp - SO dead by AI greed · Accepted Answer · 2020-06-05 13:10:45Z

42

There are two ways to do custom model validation in ASP.NET Core:

A custom attribute subclassed from ValidationAttribute. This is useful when you want to apply custom business logic to a particular model property with an attribute.
Implementing IValidatableObject for class-level validation. Use this instead when you need to do validation on an entire model at once.

The documentation has examples of both. In your case, IValidatableObject would probably be the best approach.

edited Jun 5, 2020 at 13:10

Ian Kemp - SO dead by AI greed

1

answered Jul 12, 2016 at 15:17

Nate Barbettini

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1 Comment

Justin Helgerson Over a year ago

I was looking for a custom validation section in their docs, but it looks like I missed it. Thanks!

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