Data Annotation

Is a way to validate business objects in easy and simplified manner.

using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

namespace DataAnnotations

{

    class Program

    {

        static void Main(string[] args)

        {

            Customer cust = new Customer();

            try

            {

                cust.name = "";//It will throw exception

            }

            catch(Exception ex)

            {

                Console.WriteLine(ex.Message);

            }

            cust.name = "TestName";

            cust.number = "1234567890";//here length is 11 and requird max length is 10

            ValidationContext context = new ValidationContext(cust);

            List<ValidationResult> vResults = new List<ValidationResult>();

            bool isValid = Validator.TryValidateObject(cust, context, vResults, true);

            foreach (ValidationResult vResult in vResults)

           {

                Console.WriteLine(vResult.ErrorMessage);

            }

            Console.WriteLine("Customer Validation: {0}", isValid);

        }

    }

    public class Customer

    {

        private string _name;

        //Traditional way

        public string name

        {

            get { return _name; }

            set

            {

                if (value.Length == 0)

                {

                    throw new Exception("Name is required !");

                }

                _name = value;

            }

        }

        private string _number;

        //Through data annotation

        [Required(ErrorMessage = "Number is required !")]

        [StringLength(10, ErrorMessage = "Length should be <= 10")]

        public string number

        {

            get { return _number; }

            set { _number = value; }

        }

    }

}