对集合排序的三种方式

http://www.cnblogs.com/darrenji/p/4397412.html

class Program

    {

        static void Main(string[] args)

        {

            IEnumerable<Student> result = GetStudents().OrderBy(r => r.Score);

            foreach (var item in result)

            {

                Console.WriteLine(item.Name + "--" + item.Score);

            }

            Console.ReadKey();

        }

        private static List<Student> GetStudents()

        {

            return new List<Student>()

            {

                new Student(){Id = 1, Name = "张三",Age = 15, Score = 80},

                new Student(){Id = 2, Name = "李四",Age = 16, Score = 70},

                new Student(){Id = 3, Name = "赵武",Age = 14, Score = 90}

            };

        }

    }

    public class Student 

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public int Age { get; set; }

        public int Score { get; set; }

    }

 

以上，OrderBy返回的类型是IEnumerable<Student>。

 

如果想使用List<T>的Sort方法，就需要让Student实现IComparable<Student>接口。

 

   class Program

    {

        static void Main(string[] args)

        {

            List<Student> result = GetStudents();

            result.Sort();

            foreach (var item in result)

            {

                Console.WriteLine(item.Name + "--" + item.Score);

            }

            Console.ReadKey();

        }

        private static List<Student> GetStudents()

        {

            return new List<Student>()

            {

                new Student(){Id = 1, Name = "张三",Age = 15, Score = 80},

                new Student(){Id = 2, Name = "李四",Age = 16, Score = 70},

                new Student(){Id = 3, Name = "赵武",Age = 14, Score = 90}

            };

        }

    }

    public class Student : IComparable<Student>

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public int Age { get; set; }

        public int Score { get; set; }

        public int CompareTo(Student other)

        {

          return  this.Score.CompareTo(other.Score);

        }

    }

 

让Student实现IComparable<Student>接口固然很好，如果Student是一个密封类，我们无法让其实现IComparable<Student>接口呢？不用担心，Sort方法提供了一个重载，可以接收IComparer接口类型。

 

   class Program

    {

        static void Main(string[] args)

        {

            List<Student> result = GetStudents();

            result.Sort(new StudentSorter());

            foreach (var item in result)

            {

                Console.WriteLine(item.Name + "--" + item.Score);

            }

            Console.ReadKey();

        }

        private static List<Student> GetStudents()

        {

            return new List<Student>()

            {

                new Student(){Id = 1, Name = "张三",Age = 15, Score = 80},

                new Student(){Id = 2, Name = "李四",Age = 16, Score = 70},

                new Student(){Id = 3, Name = "赵武",Age = 14, Score = 90}

            };

        }

    }

    public class Student

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public int Age { get; set; }

        public int Score { get; set; }

    }

    public class StudentSorter : IComparer<Student>

    {

        public int Compare(Student x, Student y)

        {

            return x.Score.CompareTo(y.Score);

        }

    }

 

综上，如果我们想对一个集合排序，大致有三种方式：

 

1、使用OrderBy方法，返回IEnumerable<T>类型。
2、让集合元素实现IComparable<T>接口，再使用Sort方法，返回void。
3、集合元素不实现IComparable<T>接口，针对集合元素类型写一个实现IComparer<T>接口的类，把该类实例作为Sort方法的参数。