结构型模式-过滤器模式

    public class Person
    {
        public int Age { get; set; }
        public string Name { get; set; }
        public Gender Gender { get; set; }

        public Person(int age, string name, Gender gender)
        {
            this.Age = age;
            this.Name = name;
            this.Gender = gender;
        }

        public override string ToString()
        {
            StringBuilder sb = new StringBuilder("Person{");
            sb.AppendFormat("age={0},", this.Age);
            sb.AppendFormat("name='{0}',", this.Name);
            sb.AppendFormat("gender='{0}'}", this.Gender);
            return base.ToString();
        }
    }

    public enum Gender
    {
        Male,
        Female
    }

public interface Filter
    {
        List<Person> filter(List<Person> people);
    }

    class AgeGreaterThan20Filter : Filter
    {
        public List<Person> filter(List<Person> people)
        {
            List<Person> result = new List<Person>();
            foreach (var p in people)
            {
                if (p.Age > 20)
                {
                    result.Add(p);
                }
            }
            return result;
        }
    }

    class FemaleFilter : Filter
    {
        public List<Person> filter(List<Person> people)
        {
            List<Person> result = new List<Person>();
            foreach (var p in people)
            {
                if (p.Gender == Gender.Female)
                {
                    result.Add(p);
                }
            }
            return result;
        }
    }

    class AndFilter : Filter
    {
        private Filter one;
        private Filter other;

        public AndFilter(Filter one, Filter other)
        {
            this.one = one;
            this.other = other;
        }
        public List<Person> filter(List<Person> people)
        {
            var temp = one.filter(people);
            return other.filter(temp);
        }
    }

        static void Main(string[] args)
        {
            var people = new List<Person>();
            people.Add(new Person(10,"Andy",Gender.Male));
            people.Add(new Person(25, "Cady", Gender.Male));
            people.Add(new Person(24, "Lazz", Gender.Female));

            var and = new AndFilter(new AgeGreaterThan20Filter(), new FemaleFilter());
            var p =  and.filter(people);
            Console.Read();
        }