IComparable和IComparer接口

C#中，自定义类型，支持比较和排序，需要实现IComparable接口。IComparable接口存在一个名为CompareTo()的方法，接收类型为object的参数表示被比较对象，返回整型值：1表示当前对象大于被比较对象，0表示两者相等，-1表示当前对象小于被比较对象。

public int CompareTo(object o) {}

若想以更加灵活的方式对自定义类进行比较，可以声明一个继承自IComparer接口的比较器，实现接口方法Comprae()，接收2个object类型参数作为比较对象，返回整型值：1表示前者大于后者，0表示两者相等，-1表示前者小于后者。

public int Compare(object x, object y) {}

IComparable是“可比较的”意思，自定义类实现该接口，就具有可比较的功能；IComparer是“比较器”的意思，实现该接口的类就是一个比较器，可以将比较器“注入”类中，使类具有比较和排序的功能。

IComparable接口示例代码

定义学生类，该类实现IComparable接口的CompareTo方法，该方法对Age 进行大小比较。

 1     public class Student : IComparable
 2     {
 3         public string Name { get; set; }
 4         public string Sex { get; set; }
 5         public int Age { get; set; }
 6         public int CompareTo(object obj)
 7         {
 8             Student stu = obj as Student;
 9             if (Age > stu.Age)
10             {
11                 return 1;
12             }
13             else if (Age == stu.Age)
14             {
15                 return 0;
16             }
17             else
18             {
19                 return -1;
20             }
21         }
22     }

调用List<T>.Sort方法实现stuList按照学生的年龄来排序。

 1         static void Main(string[] args)
 2         {
 3             List<Student> stuList = new List<Student>();
 4             stuList.Add(new Student() { Name = "tiana0", Sex = "Man", Age = 18 });
 5             stuList.Add(new Student() { Name = "tiana1", Sex = "Woman", Age = 20 });
 6             stuList.Add(new Student() { Name = "tiana2", Sex = "Woman", Age = 16 });
 7             stuList.Add(new Student() { Name = "tiana3", Sex = "Man", Age = 21 });
 8             stuList.Add(new Student() { Name = "tiana4", Sex = "Woman", Age = 19 });
 9             stuList.Sort();
10             foreach (Student stu in stuList)
11             {
12                 Console.WriteLine("Name=" + stu.Name + ";Sex=" + stu.Sex + ";Age=" + stu.Age);
13             }
14         }

IComparer接口示例代码

定义学生类。

 public class Student
    {
        public string Name { get; set; }
        public string Sex { get; set; }
        public int Age { get; set; }
    }

自定义比较器AgeComparer，实现接口IComparer<Student>，对学生年龄进行比较。

    public class AgeComparer : IComparer<Student>
    {
        public int Compare(Student x, Student y)
        {
            return x.Age.CompareTo(y.Age);
        }
    }

自定义比较器NameComparer，实现接口IComparer<Student>，对学生姓名进行比较。

public class NameComparer : IComparer<Student>
    {
        public int Compare(Student x, Student y)
        {
            return x.Name.CompareTo(y.Name);
        }
    }

调用List<T>.Sort方法实现stuList按照学生的年龄与姓名排序。

 1         static void Main(string[] args)
 2         {
 3             List<Student> stuList = new List<Student>();
 4             stuList.Add(new Student() { Name = "aki", Sex = "Man", Age = 18 });
 5             stuList.Add(new Student() { Name = "cki", Sex = "Woman", Age = 20 });
 6             stuList.Add(new Student() { Name = "dki", Sex = "Woman", Age = 16 });
 7             stuList.Add(new Student() { Name = "bki", Sex = "Man", Age = 21 });
 8             stuList.Add(new Student() { Name = "fki", Sex = "Woman", Age = 19 });
 9             stuList.Sort(new AgeComparer());
10             Console.WriteLine("按照年龄排序：");
11             foreach (Student stu in stuList)
12             {
13                 Console.WriteLine("Name=" + stu.Name + ";Sex=" + stu.Sex + ";Age=" + stu.Age);
14             }
15             stuList.Sort(new NameComparer());
16             Console.WriteLine();
17             Console.WriteLine("按照名称排序：");
18             foreach (Student stu in stuList)
19             {
20                 Console.WriteLine("Name=" + stu.Name + ";Sex=" + stu.Sex + ";Age=" + stu.Age);
21             }
22         }

原文链接：https://blog.csdn.net/yl2isoft/article/details/13613569