List集合排序Sort(Comparison comparison)

List< T > 集合对复杂类型的排序Sort()有4个重载
1.T类型实现了IComparable< T >接口
2.另写一个类，该类实现了IComparer< T >
3.Sort(Comparison< T > comparison),Comparison< T >为一个委托类型，CSDN定义如下：

public delegate int Comparison< T >（T x ,T y）;
// 摘要: 
    //     表示比较同一类型的两个对象的方法。
    //
    // 参数: 
    //   x:
    //     要比较的第一个对象。
    //   y:
    //     要比较的第二个对象。
    // 类型参数: 
    //   T:
    //     要比较的对象的类型。
    // 返回结果: 
    //     一个有符号整数，指示 x 与 y 的相对值，如下表所示。 值 含义 小于 0 x 小于 y。 0 x 等于 y。 大于 0 x 大于 y。

实现第三种方法的实现有3种途径：

1.定义一个方法，定义一个委托实例，将该委托实例传入Sort()中
eg.
 class Program
    {
        static void Main(string[] args)
        {
            Student sa1 = new Student(1, "Washington", 33);
            Student sa2 = new Student(2, "Brown", 32);
            Student sa3 = new Student(4, "Wade", 67);
            Student sa4 = new Student(6, "Bosh", 47);
            List  list = new List (){sa1 ,sa2 ,sa3 ,sa4 };
            Comparison comparison = new Comparison(SortByAge);//将方法传给委托实例
            list.Sort(comparison);//将委托传入Sort()

        }
        //定义一个委托类型方法
        static int SortByAge(Student x,Student y)
        {
            return x.Age.CompareTo(y.Age);
        }
    }
    public class Student
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
        public string Type { get; set; }
        public Student(int id, string name, int age)
        {
            this.ID = id;
            this.Name = name;
            this.Age = age;
        }
    }

2.使用匿名委托
eg.
 class Program
    {
        static void Main(string[] args)
        {
            Student sa1 = new Student(1, "Washington", 33);
            Student sa2 = new Student(2, "Brown", 32);
            Student sa3 = new Student(4, "Wade", 67);
            Student sa4 = new Student(6, "Bosh", 47);
            List  list = new List (){sa1 ,sa2 ,sa3 ,sa4 };
 //匿名委托delegate(Student x, Student y){return x.Name.CompareTo(y.Name);}
            list.Sort(delegate(Student x, Student y){return x.Name.CompareTo(y.Name);});
        }
        static int SortByAge(Student x,Student y)
        {
            return x.Age.CompareTo(y.Age);
        }
    }
    public class Student
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
        public string Type { get; set; }
        public Student(int id, string name, int age)
        {
            this.ID = id;
            this.Name = name;
            this.Age = age;
        }
    }

3.使用Lambda表达式
eg.
 class Program
    {
        static void Main(string[] args)
        {
            Student sa1 = new Student(1, "Washington", 33);
            Student sa2 = new Student(2, "Brown", 32);
            Student sa3 = new Student(4, "Wade", 67);
            Student sa4 = new Student(6, "Bosh", 47);
            List  list = new List (){sa1 ,sa2 ,sa3 ,sa4 };
            //lambda表达式
            list.Sort((x,y) => x.ID.CompareTo(y.ID));
                foreach (Student s in listA )
            {
                Console.WriteLine(s.ID +" " + s.Name + " " + s.Age );
            } 
        }
    }
    public class Student
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
        public string Type { get; set; }
        public Student(int id, string name, int age)
        {
            this.ID = id;
            this.Name = name;
            this.Age = age;
        }
    }