一、 对数组进行排序

最常见的排序是对一个数组排序，比如：

 int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };

 1、利用冒泡排序进行排序：

（即每个值都和它后面的数值比较，每次拿出最小值）

static void Main(string[] args)
        {
            int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };
            for (int j = 0; j < aArray.Length - 1; j++)
            {
                for (int i = 0; i < aArray.Length - 1; i++)
                {
                    if (aArray[i] > aArray[i + 1])
                    {
                        int temp = aArray[i];
                        aArray[i] = aArray[i + 1];
                        aArray[i + 1] = temp;
                    }

                }
            }


            foreach (var a in aArray)
            {
                Console.Write($"{a} ");
            }
            Console.ReadKey();
        }

运行结果：

2、利用Array.Sort排序：

1升序

 static void Main(string[] args)
        {
            int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };
            Array.Sort(aArray);

            foreach (var a in aArray)
            {
                Console.Write($"{a} ");
            }
            Console.ReadKey();
        }

运行结果：

2降序：

 先升序排列，然后对数组反转

 static void Main(string[] args)
        {
            int[] aArray = new int[8] { 18, 17, 21, 23, 11, 31, 27, 38 };
            Array.Sort(aArray);//数组排序（默认升序）
            Array.Reverse(aArray);//数组反转

            foreach (var a in aArray)
            {
                Console.Write($"{a} ");
            }
            Console.ReadKey();
        }

运行结果：

二、对List进行排序

  大多数时候，我们需要将list集合里面的数据进行排序，

1、利用List<T> 自带的Sort排序方法 

    1 、升序排序

 aList.Sort();

2、降序排序

  aList.Sort();//升序
  aList.Reverse();//反转

3 sort也可以用如下方式操作：

list.Sort((a, b) => a.CompareTo(b));//升序
list.Sort((a, b) => b.CompareTo(a));//降序

2、利用List的OrderBy与OrderByDescending方法

    升序排列：

  List<int> aList = new List<int> { 18, 17, 21, 23, 11, 31, 27, 38 };
  aList = aList.OrderBy(a => a).ToList();

降序排列：

 List<int> aList = new List<int> { 18, 17, 21, 23, 11, 31, 27, 38 };
  aList = aList.OrderByDescending(a => a).ToList();

利用link，这种感觉和方法二是一回事

List<int> aList = new List<int> { 18, 17, 21, 23, 11, 31, 27, 38 };
 aList = (from a in aList orderby a ascending select a).ToList();//升序
 aList = (from a in aList orderby a descending select a).ToList();//降序

如果集合里存放的是一个类型，比如：

学生类：

 public class Student
        {
            public string name { get; set; }
            public int age { get; set; }
            public int score { get; set; }

            public override string ToString()
            {
                return $"姓名是：{name},年龄是：{age},得分是：{score}";
            }
        }

方法一：stuList.Sort((x, y) => x.score.CompareTo(y.score));

static void Main(string[] args)
        {
            List<Student> stuList = new List<Student>
            {
                new Student() {name = "zyr", age = 23, score = 99},
                new Student() {name = "zls", age = 25, score = 95},
                new Student() {name = "zsq", age = 27, score = 100},
                new Student() {name = "zlw", age = 15, score = 69},
                new Student() {name = "ywe", age = 17, score = 72},
                new Student() {name = "asw", age = 29, score = 58}
            };

            //方法1 升序
            //stuList.Sort((x, y) => x.score.CompareTo(y.score));
     
            stuList = stuList.OrderBy(stu=>stu.score).ToList();

            foreach (var stu in stuList)
            {
                Console.WriteLine($"{stu}");
            }
            Console.ReadKey();
        }

方法二： 加入这个学生成绩有重复的，对于重复的成绩按照年龄再排序：

 方法1 升序
            stuList.Sort((x, y) =>
            {
                int ret = x.score.CompareTo(y.score);
                if (ret == 0)
                {
                    return x.age.CompareTo(y.age);
                }
                else
                {
                    return ret;
                }
            });
            方法2 升序
            stuList = stuList.OrderBy(stu => stu.score).ThenBy(stu => stu.age).ToList();