C#中的集合学习笔记

　　前言：漫长的国庆长假终于快结束了，我们该工作的工作了，该学习的学习了，该干什么的也都开始了，这篇博客我主要说一下C#中集合的使用，也就是ArrayList集合和Hashtable字典集合的使用，我在这里说的主要还是简单的使用，使学习的能够很快的学习集合然后自己研究集合的一些高级用法，在最后还列举出了一些常用的小案例。

1. ArrayList

(1) 命名空间 System.Collection

     (2)创建对象

            1)增

                   ->Add

                   ->AddRange  任何一个集合对象

                          int[] num = { 1, 2, 3, 4, 5, 6 };

                          ArrayList arr = new ArrayList();

                          //ICollection一个对象里面包含很多其他对象

                          arr.AddRange(num);

                   ->Insert

            2)删

                   ->Remove

                   ->RemoveAt

                   ->Clear

            3)改

                   ->像数组一样通过索引来修改

            4)查

                   ->Contains

                   ->IndexOf

1. 自定义集合

(1) 集合是Object类型，处理数据的时候会需要强转等操作

     (2)举例说明：

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1)新建一个Person类           class Person           {                   public string Name { get; set; }                   public int Age { get; set; }                  public char Gender { get; set; }                   public Person(string n, int a, char g)                   {                           Name = n;                           Age = a;                           Gender = g;                    }                    public void SayHello()                    {                            Console.WriteLine("我叫{0}", Name);                      }           }   2)新建一个PeresonCollection类            class PersonCollection           {                   ArrayList arr = new ArrayList();                   public void Add(Person p)                   {                            arr.Add(p);                    }                    public void AddRange(params Person[] ps)                   {                             arr.AddRange(ps);                   }                    public Person this[int index]                    {                              get { return (Person)arr[index]; }                     }                      public int Count                     {                              get { return arr.Count; }                       }           }    3)在main方法中实现           static void Main(string[] args)           {                 PersonCollection ps = new PersonCollection();                 ps.Add(new Person("韩迎龙", 23, '男'));                 ps.Add(new Person("韩全龙", 16, '男'));                 ps.Add(new Person("泛亚内", 16, '男'));                 ps.Add(new Person("野田", 16, '男'));                 for (int i = 0; i < ps.Count; i++)                 {                         ps[i].SayHello();                  }                    Console.ReadKey();           }

     (3)定义索引

            1)就是一个通过传进来的参数访问内部数据的一个属性(带有参数的属性)

            2)public 返回类型 this[索引参数类型 参数名]

              {

                   get{return 通过参数访问的数据;}

                   set{通过参数处理要修改的数据=value}

              }

              案例说明:   

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class Arr   {          int[] nums = { 10, 23, 34, 45, 56 };          public int this[int index]          {                   get {                           if (index > nums.Length - 1)                           {                                      throw new Exception("索引超出异常");                            }                     return nums[index];                    }                  set { nums[index] = value; }           }            public int Count             {                       get { return nums.Length; }              }    }    class IndexString   {         int num = 10;         string str = "字符串韩迎龙";         char ch = 'c';         public int this[int index]         {                  get { return num; }           }            public string this[string str]            {                    get { return this.str; }             }             public char this[char c]             {                        get { return ch; }               }               public string this[int n, char c, string s]               {                      get { return num + str + ch; }                }   }   class Program   {          static void Main(string[] args)          {                  IndexString IS=new IndexString();                  Console.WriteLine(IS[' ']);                  Console.WriteLine(IS[0, ' ', " "]);                   Console.ReadKey();         }   }

            3)模拟实现集合

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class MyCllection   {           ArrayList arrInt = new ArrayList();           ArrayList arrStr = new ArrayList();            ArrayList obj=new ArrayList();            public void Add(string key, object obj)            {                     int index = arrStr.Add(key);                     arrInt.Add(index);                      this.obj.Add(obj);              }              public object this[int index]               {                      get { return obj[index]; }                }               public object this[string key]               {                        get { return obj[arrStr.IndexOf(key)]; }                }   }   static void Main(string[] args)   {            MyCllection mc = new MyCllection();            mc.Add("HYL", "韩迎龙");            mc.Add("HYL", "韩全龙");            Console.WriteLine(mc[0]);            Console.WriteLine(mc["HYL"]);            Console.ReadKey();   }

1. foreach语法

　　　　(1) 执行

            1)可以只遍历一部分吗？  不能

            2)可以倒着遍历吗？      不能

            3)举例说明：

                int[] nums = { 1, 4, 6, 87, 87, 3, 23, 45 };

            foreach (int item in nums)

            {

                Console.WriteLine(item);

            }

            Console.ReadKey();

     (2)数据源应该是一个可枚举的类型(IEnumerable)

     (3)foreach循环的步骤

            1)foreach循环首先到数据集中调用GetEnumerator方法得到枚举器对象

            2)到in关键字，调用MoveNext()方法

            3)这个方法返回bool值，将枚举器移到数据集的下一个数据上，并检查是否有数据，如果有，返回true,否则返回false

            4)到临时变量(迭代变量)，开始调用枚举器的Current属性，将当前的数据取出来，然后赋值给临时变量

            5)就可以使用了

1. 嵌套类

(1) 有时候在某个类型中需要一个特定的类型处理数据，而这个类型只在当前对象类中可使用

 (2)可以将这个类定义在一个类的里面，此时称为嵌套类

(3)嵌套类的访问修饰符和一般成员一样

 (4)一般是为了考虑安全问题

1. yield迭代器

(1) 一般的语法：yield return 数据

 (2)foreach在执行开始访问数据集的时候，依旧是调用IEnumerable中的GetEnumerator方法

(3)这个Getenumerator方法可以使用这个迭代器返回数据

(4)在方法中写上循环，循环体上放上yield,那么循环不会立即结束

(5)每当执行到yield的时候就会停在那里，跳到foreach中

(6)foreach执行到in的时候，又会跳到上次停留的yield那里，继续向下执行

(7)直到下一个yield，再次调用foreach

            public IEnumerator GetEnumerator()

            {

                   for(int i=0;i<arr.Count;i++)

                   {

                          yield return arr[i];

                   }

            }

1. Hashtable 字典集合

(1) 举例说明：

           Hashtable has = new Hashtable();

            has.Add("BigBoss", "韩迎龙");

            has.Add("sdd", "的事实");

            has.Add("dfd", "的速度");

            Console.WriteLine(has["BigBoss"]);

     (2)Hashtable的使用,实现一个电子词典     

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class Program   {          static void Main(string[] args)          {                 string[] words = File.ReadAllLines("英汉词典TXT格式.txt", Encoding.Default);                 Hashtable has = new Hashtable();                  for (int i = 0; i < words.Length; i++)                  {                           string[] temp = words[i].Split(new char[] { ' '}, StringSplitOptions.RemoveEmptyEntries);                                                               if (temp.Length == 1)                             {                                    continue;                              }                                    string key = temp[0];                                    string value = string.Join(" ", temp, 1, temp.Length - 1);                                    if (!has.ContainsKey(key))                                    {                                           has.Add(key, value);                                    }                                    else                                    {                                           has[key] = string.Format("{0}\n{1}", has[i], value);                                    }                             }                             //可以查看了                             while (true)                             {                                    Console.Write("请输入单词？");                                    string str=Console.ReadLine();                                    if (has.ContainsKey(str))                                    {                                           Console.WriteLine(has[str]);                                    }                                    else                                    {                                           Console.WriteLine("很抱歉，你说查询的词汇没有找到");                                    }                             }                             Console.ReadKey();                      }               }                      static void Main(string[] args)                      {                             string[] words = File.ReadAllLines("英汉词典TXT格式.txt", Encoding.Default);                             Hashtable has = new Hashtable();                             for (int i = 0; i < words.Length; i++)                             {                                    string[] temp = words[i].Split(new char[] { ' '}, StringSplitOptions.RemoveEmptyEntries);                                    string key = temp[0];                                    string value = temp[1];                                    if (temp.Length != 2)                                    {                                           continue;                                    }                                    if (!has.ContainsKey(key))                                    {                                           has.Add(key, value);                                    }                                    else                                    {                                           has[key] = string.Format("{0}\n{1}", has[i], value);                                    }                             }                             //可以查看了                             while (true)                             {                                    Console.Write("请输入单词？");                                    string str=Console.ReadLine();                                    if (has.ContainsKey(str))                                    {                                           Console.WriteLine(has[str]);                                    }                                    else                                    {                                           Console.WriteLine("很抱歉，你说查询的词汇没有找到");                                    }                             }                             Console.ReadKey();                      }               }

     (3)如何遍历？

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static void Main(string[] args)   {               Hashtable has = new Hashtable();               has.Add("1", "韩迎龙");               has.Add("2", "得到");               //仅仅遍历key               foreach (string item in has.Keys)               {                   Console.WriteLine(item);               }               //遍历value               foreach (string item in has.Values)               {                   Console.WriteLine(item);               }               //遍历整个集合               foreach (DictionaryEntry item in has)               {                   Console.WriteLine("{0}是{1}", item.Key, item.Value); ;               }               Console.ReadKey();   }

     (4)var 类型推断

            1)var val=数据;

            2)赋什么数据就是什么类型

            3)类型确定以后就不能变了

            4)必须保证类型赋值时时确定的

            5)何时使用类型推断

                   ->匿名类型

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static void Main(string[] args)   {             var person = new { Name = "张三", Age = 23, Gender = '男' };              Console.WriteLine(person.Name);              Console.WriteLine(person.Age);               Console.WriteLine(person.Gender);               Console.ReadKey();   }

                   ->Linq查询

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static void Main(string[] args)   {               int[] nums = { 132, 454, 667, 343, 65, 76, 74 };                var query = from n in nums                                   where n > 100 && n < 500                                    select n;                foreach (var item in query)               {                      Console.WriteLine(item);               }               Console.ReadKey();   }