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

You could compare the two dates in the IsValid() method.

public class CompareDates : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        // get your StartDate and EndDate from model and value

        // perform comparison
        if (StartDate < EndDate)
        {
            return new ValidationResult("start date must be less than the end date");
        }
        else
        {
            return ValidationResult.Success;
        }
    }
}