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最全数据结构详述: List VS IEnumerable VS IQueryable VS ICollection VS IDictionary

葡萄城控件

发布于 2018-01-10 05:14:03

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文章被收录于专栏：葡萄城控件技术团队葡萄城控件技术团队

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代码可运行

本文对常用的数据结构详述：Array, ArrayList，List，IList，ICollection, Stack, Queue, HashTable, Dictionary, IQueryable, IEnumerable。

Collection（集合）

Collection是数据记录集合，

编写代码过程中，常常需要合适的容器保存临时数据，方便修改和查找，如何选取合适的数据容器，关键在于将执行的数据操作以及数据记录是否大量。

Array（数组）

特征

1. 固定大小，数组的大小是初始化时决定无法修改的数值。

2. 强类型，存储数据元素类型必须在初始化时指定，因此在运行时，不需要耗费额外的时间来定义数组类型，能够大大提升运行效率。

3. 可使用Foreach关键字实现数组迭代和查找。

因为数组大小是固定的，且是强类型数据结构，因此在运行时只占用很少的内存，运行时效率很高。

       //It is obvious that strArray is
       //1. string   --> Strongly Type
       //2. Sized=10 --> Fixed Size
     
        string[] strArray = new string[10];
     
           for (int i = 0; i < 10; i++)
           {
            if (strArray[i]==null)
              {
                  strArray[i] = (i+1).ToString();
              }
          }
     
          this.ListBoxArray.DataSource = null;
          this.ListBoxArray.Items.Clear();
     
          this.ListBoxArray.DataSource = strArray;
          this.ListBoxArray.DataBind();

ArrayList

1. ArrayList 没有固定的长度，容量可动态增加，可应用于开发人员无法确定数组元素个数等场景，当然这种情况下，在定义结构体的时候会非常耗时。

2. ArrayList 不是强类型，ArrayList中不同元素类型可以不相同，并且需要在运行时根据实际的输入来确定元素类型。因此在运行时消耗内存较多。

3. 可使用Froeach 关键字操作ArrayList。

public class Product
         {
             public Product()
             {
             
             }
             public Product(string Code, string Name)
             {
                 _Code = Code;
                 _Name = Name;
             }
     
                public string _Code {get; set;}
                public string _Name { get; set; }
        }

ArrayList支持String,int,以及十进制小数类型。

   //It is NOT obvious that strArrayList is 1. string? int? object? decimal?  --> NOT Strongly Type
   //                                       2. Sized=10? 20? 100?             -->NOT Fixed Size
   // Namespace: System.Collections
      
   System.Collections.ArrayList strArrayList = new System.Collections.ArrayList();
   //System.Linq.IQueryable  type of data is not specific runtime defered support
   strArrayList.Add("Mahsa");  //   "Mahsa": is string
   strArrayList.Add(1);        //        1 : is integer
   strArrayList.Add(0.89);     //      0.89: is decimal
     
     this.ListBoxArrayList.DataSource = null;
     this.ListBoxArrayList.Items.Clear();
     this.ListBoxArrayList.DataSource = strArrayList;
     this.ListBoxArrayList.DataBind();
     
     System.Text.StringBuilder str= new System.Text.StringBuilder();
     
     foreach (var item in strArrayList)
     {
         str.Append(" , "+item);
     }
     this.lblArrayList.Text = str.ToString();
     
     //Below is old way to fill obj from product , in Arraylist you need to create more than one instance
    // Product objProduct = new Product();
    // objProduct.Code = "1001";
    // objProduct.Name = "Chair";
     
     //It is NOT obvious that strArrayList is
     //1. string? int? object? decimal? OR OBJECT??  --> NOT Strongly Type   //2. Sized=10? 20? 100?                         -->NOT Fixed Size
     // Namespace: System.Collections   
     System.Collections.ArrayList objArrayList = new System.Collections.ArrayList();
     
     objArrayList.Add(new Product("1001", "Chair"));
     objArrayList.Add(new Product("1002", "Sofa"));
     objArrayList.Add(new Product("1003", "Carpet"));
     
     this.DropDownListArrayListObject.DataSource = null;
     this.DropDownListArrayListObject.Items.Clear();
     this.DropDownListArrayListObject.DataSource = objArrayList;
     
     //* Finding among Object of Array List is difficult , you have to find your specific item by index
     Product objTemp = (Product)objArrayList[0];
     objArrayList.Remove(objTemp);
     //*
     this.DropDownListArrayListObject.DataTextField = "_Name";
     this.DropDownListArrayListObject.DataValueField = "_Code";
     this.DropDownListArrayListObject.DataBind();
     this.GridViewArrayListObject.DataSource = objArrayList;
     this.GridViewArrayListObject.DataBind();

HashTable（哈希表）

HashTable是一种定义关键字的数据结构体，使用哈希表查找数据非常方便，哈希表既不是强类型也不固定大小限制。

            //It is NOT obvious that strArrayList is
           //1. string? int? object? decimal? OR OBJECT??  --> NOT Strongly Type
           //2. Sized=10? 20? 100?                         -->NOT Fixed Size
           // Namespace: System.Collections
           //Hashtable solve the problem in Arraylist when we are looking for specific item
           //Hashtable dedicate a key for each item, then finding item is easier and faster
     
            System.Collections.Hashtable objHashTable = new System.Collections.Hashtable();
     
            objHashTable.Add("1001","Chair");
            objHashTable.Add("1002", "Sofa");
            objHashTable.Add("1003", "Carpet");   
     
           this.DropDownListHashTable.DataSource = null;
           this.DropDownListHashTable.Items.Clear();
           this.DropDownListHashTable.DataSource = objHashTable;
           //* finding item is easier you just need to point to it by call its key
           objHashTable.Remove("1002");
           //*
           this.DropDownListHashTable.DataTextField = "Value";
           this.DropDownListHashTable.DataValueField = "Key";
           this.DropDownListHashTable.DataBind();

Stack

栈是最典型的数据结构，栈具有优先级划分的数据结构，栈为每个内容项定义优先级，表示每个Item入栈和出栈的优先顺序。因此操作栈中的数据，需要先将数据push 到栈的顶部，需要删除元素必须变成栈顶部，即要遵守后进先出（LIFO）的原则。

栈与哈希表一样既不是强类型也不限制元素个数。

Push 操作

            //Stack is LIFO: Last in First Out
            System.Collections.Stack objStackPush = new System.Collections.Stack();
     
            //By Push method you can insert item at the top of the stack
            objStackPush.Push("Mahsa");
            objStackPush.Push("Hassankashi");
            this.lblPop.Text = "";
            this.ListBoxStack.DataSource = objStackPush.ToArray();
            this.ListBoxStack.DataBind();

Pop操作

    System.Collections.Stack objStackPop = new System.Collections.Stack();
    
    objStackPop.Push("Mahsa");
    objStackPop.Push("Hassankashi");  
     
    //By Pop method you can remove item from the top of the stack --> Last in First in
    this.lblPop.Text = objStackPop.Pop().ToString();
      
    this.ListBoxStack.DataSource = objStackPop.ToArray();
    this.ListBoxStack.DataBind();

Queue

Queue同栈一样也是具有优先级定义的结构体，遵循的规则是先进先出（FIFO），既不是强类型也不具有固定的大小限制。

入队操作

      //Queue is FIFO: First in First Out
     System.Collections.Queue objQueue = new System.Collections.Queue();
      
     //By Enqueue method you can insert item at the END of the Queue
     objQueue.Enqueue("Mahsa");
     objQueue.Enqueue("Hassankashi");
     objQueue.Enqueue("Cosmic");
     objQueue.Enqueue("Verse");
     
     this.lblQueue.Text = "";
     this.ListBoxQueue.DataSource = objQueue.ToArray();
     this.ListBoxQueue.DataBind();

出队操作

   1:  System.Collections.Queue objQueue = new System.Collections.Queue();
   2:   
   3:  objQueue.Enqueue("Mahsa");
   4:  objQueue.Enqueue("Hassankashi");
   5:  objQueue.Enqueue("Cosmic");
   6:  objQueue.Enqueue("Verse");
   7:   
   8:  //By Dequeue method you can remove item from the BEGINING of the Queue --> First in First out FIFO
   9:  this.lblQueue.Text=objQueue.Dequeue().ToString();
  10:   
  11:  this.ListBoxQueue.DataSource = objQueue.ToArray();
  12:  this.ListBoxQueue.DataBind();

入队操作

   1:  System.Collections.Queue objQueue = new System.Collections.Queue();
   2:   
   3:  objQueue.Enqueue("Mahsa");
   4:  objQueue.Enqueue("Hassankashi");
   5:  objQueue.Enqueue("Cosmic");
   6:  objQueue.Enqueue("Verse");
   7:   
   8:  //By Dequeue method you can remove item from the BEGINING of the Queue --> First in First out FIFO
   9:  this.lblQueue.Text=objQueue.Dequeue().ToString();
  10:   
  11:  this.ListBoxQueue.DataSource = objQueue.ToArray();
  12:  this.ListBoxQueue.DataBind();

什么情况下需要使用List？

1. List长度可不固定

2. 当数据为通用类型，List是强类型，List中元素类型不需要等到运行时来确定，这种特性使得List 运行时效率非常高。

3. 可使用Foreach关键字。

因为List不需要设定固定的大小，List灵活度高，且效率高常用于开发过程中。

   1:  //Like Array is Strong Type
   2:  //Like ArrayList with No Dimension
   3:  System.Collections.Generic.List<string> strList = new List<string>();
   4:   
   5:   
   6:  strList.Add("Mahsa");
   7:  strList.Add("Hassankashi");
   8:  strList.Add("Cosmic");
   9:  strList.Add("Verse");
  10:   
  11:  this.ListBoxListGeneric.DataSource = strList;
  12:  this.ListBoxListGeneric.DataBind();
  13:   
  14:  System.Text.StringBuilder str = new System.Text.StringBuilder();
  15:   
  16:  foreach (var item in strList)
  17:  {
  18:      str.Append(" , " + item);
  19:  }
  20:  this.lblList.Text = str.ToString();

IList

IList 继承了List，包含多种方法的List接口。如果你无法判断代码改动的可能性，可以使用IList接口，减少模块之间的依赖性。IList是接口因此无法被实例化，所以必须使用List来初始化。

   1:  System.Collections.Generic.IList<string> strIList = new List<string>();

我们一起了解一下具体的类和接口之间的区别。

1. 具体类可继承其他类，并实现一个或多个接口。

2. 在内部类中可以定义变量并赋值，接口中不允许此操作。

3. 具体类可包含构造函数，而接口中不能定义构造函数

4. 抽象类中可包含访问修饰符如public,private等，接口中不能包含。

   1:  //Ilist can not be instantiate from Ilist , so it should be instantiate from List
   2:  System.Collections.Generic.IList<string> strIList = new List<string>();
   3:   
   4:  strIList.Add("Mahsa");
   5:  strIList.Add("Hassankashi");
   6:  strIList.Add("Cosmic");
   7:  strIList.Add("Verse");
   8:   
   9:   
  10:  this.ListBoxListGeneric.DataSource = strIList;
  11:  this.ListBoxListGeneric.DataBind();
  12:   
  13:  System.Text.StringBuilder str = new System.Text.StringBuilder();
  14:   
  15:  foreach (var item in strIList)
  16:  {
  17:      str.Append(" , " + item);
  18:  }
  19:  this.lblList.Text = str.ToString();

IEnumerable

IEnumerable常用于遍历集合元素，但是无法修改（删除或添加）数据，使用IEnumberable 会从服务器端将所有数据拷贝到客户端，并进行一定的过滤，如果服务器端有大量数据会造成内存负载超重。

   1:  //IEnumerable can not be instantiate from Enumerable , so it should be instantiate from List
   2:         System.Collections.Generic.IEnumerable<Employee> empIEnumerable = new List<Employee>
   3:         {   new Employee { ID = 1001, Name="Mahsa"},
   4:             new Employee { ID = 1002, Name = "Hassankashi" },
   5:             new Employee { ID = 1003, Name = "CosmicVerse" },
   6:             new Employee { ID = 1004, Name = "Technical" }
   7:         };
   8:   
   9:   
  10:         this.GridViewIEnumerable.DataSource = empIEnumerable;
  11:         this.GridViewIEnumerable.DataBind();
  12:   
  13:         System.Text.StringBuilder str = new System.Text.StringBuilder();
  14:   
  15:         foreach (Employee item in empIEnumerable)
  16:         {
  17:             str.Append(" , " + item.ID +"-"+item.Name);
  18:         }
  19:   
  20:         this.lblIEnumerable.Text = str.ToString();

IQueryable

IQueryable与IEnumberable不同的是，当从服务器端加载过量的数据，IQueryable会自动减少应用负载。IQueryable可保证大数据量时应用程序的高性能。

IQueryable会先过滤数据，然后发送给客户端。

   1:  DataAccessEntities ctx = new DataAccessEntities();
   2:          var ctx = new DataAccessEntities();

   1:  //Difference between IQueryable and IEnumerable
   2:   
   3:          //You can instantiate IEnumerable from List
   4:   
   5:          IEnumerable<employee> queryIEnumerable = new List<employee>() ;
   6:   
   7:   
   8:          //Bring  ALL records from server --> to client then filter collection
   9:         //To bring all data from server you should omit where cluse from linq to sql 
   10:          queryIEnumerable = from m in ctx.Employees select m;
   11:   
   12:          //If you use where as extension method with IEnumerable then All records will be loaded 
   13:          queryIEnumerable = queryIEnumerable.Where(x => x.ID == 1).ToList();
   14:        
   15: 
   16:   
   17:          //You can not instantiate IQueryable
   18:   
   19:          IQueryable<employee> queryIQueryable=null;
   20:  
   21:          //Bring just ONE record from server --> to client
   22:   
   23:          queryIQueryable = (from m in ctx.Employees
   24:                       where m.ID == 1
   25:                       select m);
   26:   
   27:          //Whenever you call IQueryable so ==> It will be executed 
   28:          this.GridViewIQueryable.DataSource = queryIQueryable.ToList();
   29:          this.GridViewIQueryable.DataBind();
   30:  </employee>

SQL Profiler:

如何追踪查询语句生成TSQL，生成需要的数据结构体：

Step 1:

Start -> MS SQL Server 2008 -> Performance Tools -> SQL Server Profiler

Step 2:

SQL Server Profiler -> File -> New Trace

Step 3:

输入连接数据库的用户名和密码

Step 4:

General (Tab) -> Use the Template: Standard

Step 5:

Event Selection (Tab) -> Event : TSQL -> Select : SQL-BatchCompleted | Select Show all Columns

Press Column Filter -> Database Name: Like: "DataAccess"

运行

Step 6:

查看结果

Step 7:

生成 IEnumerable数据 :

   1:  SELECT 
   2:  [Extent1].[ID] AS [ID], 
   3:  [Extent1].[Name] AS [Name], 
   4:  [Extent1].[Age] AS [Age]
   5:  FROM [dbo].[Employee] AS [Extent1]

生成 IQueryable :

SELECT 
[Extent1].[ID] AS [ID], 
[Extent1].[Name] AS [Name], 
[Extent1].[Age] AS [Age]
FROM [dbo].[Employee] AS [Extent1]
WHERE 1 = [Extent1].[ID]

ICollection 继承了IEnumberable，但是IEnumberable是基于索引的，ICollection不基于索引。

   1:  //IList {indexer and Modify} vs ICollection {randomly and Modify}
   2:   //Collection can not be instantiate from ICollection , so it should be instantiate from List
   3:   System.Collections.Generic.ICollection<string> strICollection = new List<string>();
   4:   strICollection.Add("Mahsa");
   5:   strICollection.Add("Hassankashi");
   6:   
   7:   //Countable***
   8:   int ICollectionCount=strICollection.Count;
   9:   
  10:   this.ListBoxICollection.DataSource = strICollection;
  11:   this.ListBoxICollection.DataBind();
  12:   System.Text.StringBuilder str = new System.Text.StringBuilder();
  13:   foreach (var item in strICollection)
  14:   {
  15:       str.Append(" , " + item);
  16:   }
  17:   this.lblICollection.Text = str.ToString();
  18:   
  19:   //IList***
  20:   System.Collections.Generic.IList<Employee> objIList = new List<Employee>();
  21:   objIList = (from m in ctx.Employees
  22:               select m).ToList();
  23:   
  24:  Employee obj = objIList.Where(i => i.Name == "Sara").FirstOrDefault();
  25:  int indexofSara= objIList.IndexOf(obj);
  26:  int cIList = objIList.Count;
  27:   
  28:   //ICollection***
  29:   System.Collections.Generic.ICollection<Employee> objICollection = new List<Employee>();
  30:   objICollection = (from m in ctx.Employees
  31:                     select m).ToList();
  32:   Employee objIC = objICollection.Where(i => i.Name == "Sara").FirstOrDefault();
  33:   //You can not get index of object , if you clear comment from below code appears error
  34:  // int indexofSaraICollection = objIC.IndexOf(objIC);
  35:   int cICollection = objICollection.Count;

入栈：

   1:  //Stack is LIFO: Last in First Out
   2:         //Here is for Push Stack in Generic
   3:         //System.Collections.Stack objStackPush = new System.Collections.Stack();
   4:         //Stack<T> can be instantiated from Stack<T>
   5:   
   6:         System.Collections.Generic.Stack<int> objStackPush = new System.Collections.Generic.Stack<int>();
   7:   
   8:         objStackPush.Push(1);
   9:         objStackPush.Push(2);
  10:   
  11:         this.lblPopGeneric.Text = "";
  12:         this.ListBoxStackGeneric.DataSource = objStackPush.ToArray();
  13:         this.ListBoxStackGeneric.DataBind();

出栈：

   1:  //Stack is LIFO: Last in First Out
   2:         //Here is for Pop Stack in Generic
   3:         //System.Collections.Stack objStackPop = new System.Collections.Stack();
   4:         //Stack<T> can be instantiated from Stack<T>
   5:   
   6:         System.Collections.Generic.Stack<int> objStackPop = new System.Collections.Generic.Stack<int>();
   7:   
   8:         objStackPop.Push(1);
   9:         objStackPop.Push(2);
  10:   
  11:         this.lblPop.Text = objStackPop.Pop().ToString();
  12:         this.ListBoxStack.DataSource = objStackPop.ToArray();
  13:         this.ListBoxStack.DataBind();

Queue Generic

入队：

   1:  //Queue is FIFO: First in First Out
   2:         //Here is for Enqueue Queue in Generic
   3:         //System.Collections.Queue objQueue = new System.Collections.Queue();
   4:         //Queue<T> can be instantiated from Queue<T>
   5:   
   6:         System.Collections.Generic.Queue<int> objQueue = new System.Collections.Generic.Queue<int>();
   7:         objQueue.Enqueue(1);
   8:         objQueue.Enqueue(2);
   9:   
  10:         this.lblQueue.Text = "";
  11:   
  12:         this.ListBoxQueue.DataSource = objQueue.ToArray();
  13:         this.ListBoxQueue.DataBind();

出队：

   1:  //Queue is FIFO: First in First Out
   2:         //Here is for Enqueue Queue in Generic
   3:         //System.Collections.Queue objQueue = new System.Collections.Queue();
   4:         //Queue<T> can be instantiated from Queue<T>
   5:   
   6:         System.Collections.Generic.Queue<int> objQueue = new System.Collections.Generic.Queue<int>();
   7:         objQueue.Enqueue(1);
   8:         objQueue.Enqueue(2);
   9:   
  10:         this.lblQueue.Text = "";
  11:   
  12:         this.ListBoxQueue.DataSource = objQueue.ToArray();
  13:         this.ListBoxQueue.DataBind();

Dictionary 及 IDictionary：

Dictionary 可通用，而哈希表不是通用的。Dictionary定义 <TKey，Tvalue>。IDictionary是Dictionary的接口，如果在后期开发中需要大量修改，建议使用IDictionary。

//Dictionary can instantiate from Dictionary , Dictionary is similar to Hashtable,
//Dictionary is GENERIC but Hashtable is NON GENERIC
//Such Hashtable you can find object by its key
System.Collections.Generic.Dictionary<int, string=""> objDictionary = new Dictionary<int, string="">();

objDictionary.Add(1001, "Mahsa");
objDictionary.Add(1002, "Hassankashi");
objDictionary.Add(1003, "Cosmicverse");

string str = objDictionary[1002];

this.ListBoxDictionary.DataSource = objDictionary;
this.ListBoxDictionary.DataBind();</int,>