Custom Validation Attributes: Comparing two properties in the same model

Question

Is there a way to create a custom attribute in ASP.NET Core to validate if one date property is less than other date property in a model using ValidationAttribute<

Answer 1

As one possible option self-validation:

You just need to Implement an interface IValidatableObject with the method Validate(), where you can put your validation code.

public class MyViewModel : IValidatableObject
{
    [Required]
    public DateTime StartDate { get; set; }

    [Required]
    public DateTime EndDate { get; set; } = DateTime.Parse("3000-01-01");

    public IEnumerable Validate(ValidationContext validationContext)
    {
        int result = DateTime.Compare(StartDate , EndDate);
        if (result < 0)
        {
            yield return new ValidationResult("start date must be less than the end date!", new [] { "ConfirmEmail" });
        }
    }
}