C#特性类的使用

public class Order
    {
        [StringLength("订单号", 6, MinLength = 3, ErrorMessage = "{0}的长度必须在{1}和{2}之间！")]//实例化一个特性类，关联到一个字段上面
        public string OrderID { get; set; }
    }

class Program
    {
        #region 使用特性类的过程

        //验证过程
        //1.通过映射，找到成员属性关联的特性类实例，
        //2.使用特性类实例对新对象的数据进行验证

        //用特性类验证订单号长度
        public static bool isIDLengthValid(int IDLength, MemberInfo member)
        {
            foreach (object attribute in member.GetCustomAttributes(true)) //2.通过映射，找到成员属性上关联的特性类实例，
            {
                if (attribute is StringLengthAttribute)//3.如果找到了限定长度的特性类对象，就用这个特性类对象验证该成员
                {
                    StringLengthAttribute attr = (StringLengthAttribute)attribute;
                    if (IDLength < attr.MinLength || IDLength > attr.MaxLength)
                    {
                        string displayName = attr.DisplayName;
                        int maxLength = attr.MaxLength;
                        int minLength = attr.MinLength;
                        string error = attr.ErrorMessage;
                        Console.WriteLine(error, displayName,maxLength, minLength);//验证失败，提示错误
                        return false;
                    }
                    else return true;
                }
               
            }
            return false;
        }


        //验证订单对象是否规范
        public static bool isOrderValid(Order order)
        {
            if (order == null) return false;
            foreach (PropertyInfo p in typeof(Order).GetProperties())
            {
                if (isIDLengthValid(order.OrderID.Length, p))//1记录下新对象需要验证的数据，
                    return true;
            }
            return false;

        }
        #endregion
        public static void Main()
        {
            Order order=new Order();
            do
            {
                Console.WriteLine("请输入订单号：");
                 order.OrderID= Console.ReadLine();
            }
            while (!isOrderValid(order));
            Console.WriteLine("订单号输入正确，按任意键退出！");
            Console.ReadKey();
        }

    }