asp.net-coreModels

Model Validation with Validation Attrributes

Validation attributes can be used to easily configure model validation.

public class MyModel
{
    public int id { get; set; }

    //sets the FirstName to be required, and no longer than 100 characters
    [Required]
    [StringLength(100)]
    public string FirstName { get; set; }
}

The built in attributes are:

  • [CreditCard]: Validates the property has a credit card format.
  • [Compare]: Validates two properties in a model match.
  • [EmailAddress]: Validates the property has an email format.
  • [Phone]: Validates the property has a telephone format.
  • [Range]: Validates the property value falls within the given range.
  • [RegularExpression]: Validates that the data matches the specified regular expression.
  • [Required]: Makes a property required.
  • [StringLength]: Validates that a string property has at most the given maximum length.
  • [Url]: Validates the property has a URL format.

Model Validation with Custom Attribute

If the built in attributes are not sufficient to validate your model data, then you can place your validation logic in a class derived from ValidationAttribute. In this example only odd numbers are valid values for a model member.

Custom Validation Attribute

public class OddNumberAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        try
        {
            var number = (int) value;
            if (number % 2 == 1)
                return ValidationResult.Success;
            else
                return new ValidationResult("Only odd numbers are valid.");
        }
        catch (Exception)
        {
            return new ValidationResult("Not a number.");
        }            
    }
}

Model Class

public class MyModel
{
    [OddNumber]
    public int Number { get; set; }
}