C#中对集合排序的三种方式

ゞ浴缸里的玫瑰 2024-04-03 09:29 45阅读 0赞

对集合排序，可能最先想到的是使用OrderBy方法。

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。

来源：作者博客-《[医院证明模板][Link 1]》

[Link 1]: http://www.chiniurou.com/