C#自定义类型数组排序

在数组或者集合中对自定义类型进行排序分为两种方法。

1.如果这个自定义类型是自己定义编写的，那么我可以使它继承ICompareable<T>接口，实现其中的CompareTo(Object)方法。然后直接Array.Sort(排序对象数组)对其进行排序。

     class Book: IComparable<Book>
     {
         //defined name and number for book
         public string BookName { get; set; }
         public string BookNo { get; set; }
         // implement the CompareTo method
         public int CompareTo(Book other)
         {
             if (other == null) throw new ArgumentNullException("other");
             // compare to BookNo
             return this.BookNo.CompareTo(other.BookNo);
         }
     }

我自定义了一个Book类型。有BookName和BookNo属性。我使它继承了ICompareable<Book>接口。并且实现了CompareTo(Book)方法。这样，我就可以直接用Array.Sort()对

这个数组按BookNo进行排序。

        static void test2()
         {
             Book[] bookArray = {
                                    new Book{BookName = "AAA",BookNo = ""},
                                    new Book{BookName = "DDD",BookNo = ""},
                                    new Book{BookName = "CCC",BookNo = ""},
                                    new Book{BookName = "BBB",BookNo = ""},
                                };
             Array.Sort(bookArray);
             foreach (Book item in bookArray)
             {
                 Console.WriteLine("BookName = \"{0}\"; BookNo = \"{1}\".",item.BookName,item.BookNo);
             }

         }

输出结果：

BookName = "AAA"; BookNo = "".
BookName = "BBB"; BookNo = "".
BookName = "CCC"; BookNo = "".
BookName = "DDD"; BookNo = "".

2.如果这个自定义类型不是自己编写的，是别人已经编写好的的一个类型，我不能修改这个类型。或者我想按照BookName排序，但是还不能修改现有的Book类该怎么办？

我们可以对这个类型进行包装。

     class Person
     {
         public string PersonName { get; set; }
         public string PersonAge {get;set;}
     }

Person这个类型没有继承ICompare接口。这个类不能修改，但是我还要对PersonAge进行排序。

我自己创建一个PersonCompare类，它实现了ICompare<T>接口，我把排序规则写在这个类中。

     class PersonCompare : IComparer<Person>
     {
         public int Compare(Person x, Person y)
         {
             if (x == null || y == null) throw new ArgumentNullException("argument error.");
             return x.PersonAge.CompareTo(y.PersonAge); //sort rule
         }
     }

测试：

        static void test3()
         {
             Person[] personArray = {
                                        new Person{PersonName = "AAA",PersonAge = ""},
                                        new Person{PersonName = "EEE",PersonAge = ""},
                                        new Person{PersonName = "CCC",PersonAge = ""},
                                        new Person{PersonName = "FFF",PersonAge = ""},
                                    };
             Array.Sort(personArray,new PersonCompare());//second parameter is sort rule
             foreach(Person item in personArray)
             {
                 Console.WriteLine("PersonName = \"{0}\"; PersonAge = \"{1}\".", item.PersonName, item.PersonAge);
             }
         }

输出结果：

PersonName = "AAA"; PersonAge = "".
PersonName = "CCC"; PersonAge = "".
PersonName = "EEE"; PersonAge = "".
PersonName = "FFF"; PersonAge = "".

扩展：

如果我想对指定的属性进行排序怎么办？比如有的同事需要用PersonAge进行排序，有的需要使用PersonName进行排序。这种需求很常见。我们修改下PersonCompare方法。

为了使代码更加的规范。我建议以Person的属性为基础创建一个枚举。这个enum控制着我要按照那个属性进行排序。

    enum PersonType
     {
         PersonName,
         PersonAge
     }

我们需要PersonType作为参数传递给PersonCompare。以实现根据需求来定制排序规则。

   class PersonCompare : IComparer<Person>
    {
        private PersonType useType;
        public PersonCompare(PersonType pt)
        {
            this.useType = pt;
        }
        public int Compare(Person x, Person y)
        {
            if (x == null || y == null) throw new ArgumentNullException("argument error.");
            //return x.PersonAge.CompareTo(y.PersonAge);
            switch (useType){
                case PersonType.PersonAge:
                    return x.PersonAge.CompareTo(y.PersonAge);
                case PersonType.PersonName:
                    return x.PersonName.CompareTo(y.PersonName);
                default :
                    throw new ArgumentNullException("Doesn't contain this type.");
            }
        }
    }

测试：

        static void test3()
         {
             Person[] personArray = {
                                        new Person{PersonName = "AAA",PersonAge = ""},
                                        new Person{PersonName = "EEE",PersonAge = ""},
                                        new Person{PersonName = "CCC",PersonAge = ""},
                                        new Person{PersonName = "FFF",PersonAge = ""},
                                    };
             Array.Sort(personArray,new PersonCompare(PersonType.PersonAge));// sort by age
             foreach(Person item in personArray)
             {
                 Console.WriteLine("PersonName = \"{0}\"; PersonAge = \"{1}\".", item.PersonName, item.PersonAge);
             }
             Console.WriteLine("---------------------------------------------------");
             Array.Sort(personArray, new PersonCompare(PersonType.PersonName)); // sort by name
             foreach (Person item in personArray)
             {
                 Console.WriteLine("PersonName = \"{0}\"; PersonAge = \"{1}\".", item.PersonName, item.PersonAge);
             }
         }

输出结果：

PersonName = "CCC"; PersonAge = "".
PersonName = "AAA"; PersonAge = "".
PersonName = "EEE"; PersonAge = "".
PersonName = "FFF"; PersonAge = "".
---------------------------------------------------
PersonName = "AAA"; PersonAge = "".
PersonName = "CCC"; PersonAge = "".
PersonName = "EEE"; PersonAge = "".
PersonName = "FFF"; PersonAge = "".

总结：

其实数组和集合的排序一样。如果对自己定义的类型数组或者集合排序就用IComareable<T>。如果要对已有的类型数组或者集合排序就用IComare<T>.