Question

I am new about attributes. I just try it on my console application.

So how can i validate my person instance below example ?

class Person
    {
        [StringLength(8,ErrorMessage="Please less then 8 character")]
        public string Name { get; set; }

    }

Answer 1

Here is simple code example without reflection.

class Program
{
    static void Main(string[] args)
    { 
        var invalidPerson = new Person { Name = "Very long name" };
        var validPerson = new Person { Name = "1" };

        var validator = new Validator<Person>();

        Console.WriteLine(validator.Validate(validPerson).Count);
        Console.WriteLine(validator.Validate(invalidPerson).Count);

        Console.ReadLine();
    }
}

public class Person
{
    [StringLength(8, ErrorMessage = "Please less then 8 character")]
    public string Name { get; set; }
}

public class Validator<T> 
{
    public IList<ValidationResult> Validate(T entity)
    {
        var validationResults = new List<ValidationResult>();
        var validationContext = new ValidationContext(entity, null, null);
        Validator.TryValidateObject(entity, validationContext, validationResults, true);
        return validationResults;
    }
}