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

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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。

 1: //It is obvious that strArray is

 2:  //1. string   --> Strongly Type

 3:  //2. Sized=10 --> Fixed Size

 4:  

 5:  string[] strArray = new string[10];

 6:  

 7:  for (int i = 0; i < 10; i++)

 8:  {

 9:  if (strArray[i]==null)

 10:  {

 11:  strArray[i] = (i+1).ToString();

 12:  }

 13:  }

 14:  

 15:  this.ListBoxArray.DataSource = null;

 16:  this.ListBoxArray.Items.Clear();

 17:  

 18:  this.ListBoxArray.DataSource = strArray;

 19:  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。

 1: public class Product

 2:  {

 3:  public Product()

 4:  {

 5: 

 6:  }

 7:  public Product(string Code, string Name)

 8:  {

 9:  _Code = Code;

 10:  _Name = Name;

 11:  }

 12:  

 13:  public string _Code {get; set;}

 14:  public string _Name { get; set; }

 15:  }

ArrayList支持String,int,以及十进制小数类型。

 1: //It is NOT obvious that strArrayList is 1. string? int? object? decimal?  --> NOT Strongly Type

 2:  //                                       2. Sized=10? 20? 100?             -->NOT Fixed Size

 3:  // Namespace: System.Collections

 4:  

 5:  System.Collections.ArrayList strArrayList = new System.Collections.ArrayList();

 6:  //System.Linq.IQueryable  type of data is not specific runtime defered support

 7:  strArrayList.Add("Mahsa"); //   "Mahsa": is string

 8:  strArrayList.Add(1); //        1 : is integer

 9:  strArrayList.Add(0.89); //      0.89: is decimal

 10:  

 11:  this.ListBoxArrayList.DataSource = null;

 12:  this.ListBoxArrayList.Items.Clear();

 13:  this.ListBoxArrayList.DataSource = strArrayList;

 14:  this.ListBoxArrayList.DataBind();

 15:  

 16:  System.Text.StringBuilder str= new System.Text.StringBuilder();

 17:  

 18:  foreach (var item in strArrayList)

 19:  {

 20:  str.Append(" , "+item);

 21:  }

 22:  this.lblArrayList.Text = str.ToString();

 23:  

 24:  //Below is old way to fill obj from product , in Arraylist you need to create more than one instance

 25: // Product objProduct = new Product();

 26: // objProduct.Code = "1001";

 27: // objProduct.Name = "Chair";

 28:  

 29:  //It is NOT obvious that strArrayList is

 30:  //1. string? int? object? decimal? OR OBJECT??  --> NOT Strongly Type

 31:  //2. Sized=10? 20? 100?                         -->NOT Fixed Size

 32:  // Namespace: System.Collections

 33:  

 34:  System.Collections.ArrayList objArrayList = new System.Collections.ArrayList();

 35:  

 36:  objArrayList.Add(new Product("1001", "Chair"));

 37:  objArrayList.Add(new Product("1002", "Sofa"));

 38:  objArrayList.Add(new Product("1003", "Carpet"));

 39:  

 40:  this.DropDownListArrayListObject.DataSource = null;

 41:  this.DropDownListArrayListObject.Items.Clear();

 42:  this.DropDownListArrayListObject.DataSource = objArrayList;

 43:  

 44:  //* Finding among Object of Array List is difficult , you have to find your specific item by index

 45:  Product objTemp = (Product)objArrayList[0];

 46:  objArrayList.Remove(objTemp);

 47:  //*

 48:  this.DropDownListArrayListObject.DataTextField = "_Name";

 49:  this.DropDownListArrayListObject.DataValueField = "_Code";

 50:  this.DropDownListArrayListObject.DataBind();

 51:  this.GridViewArrayListObject.DataSource = objArrayList;

 52:  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。

 1: //It is NOT obvious that strArrayList is

 2:  //1. string? int? object? decimal? OR OBJECT??  --> NOT Strongly Type

 3:  //2. Sized=10? 20? 100?                         -->NOT Fixed Size

 4:  // Namespace: System.Collections

 5:  //Hashtable solve the problem in Arraylist when we are looking for specific item

 6:  //Hashtable dedicate a key for each item, then finding item is easier and faster

 7:  

 8:  System.Collections.Hashtable objHashTable = new System.Collections.Hashtable();

 9:  

 10:  objHashTable.Add("1001","Chair");

 11:  objHashTable.Add("1002", "Sofa");

 12:  objHashTable.Add("1003", "Carpet");

 13:  

 14:  

 15:  this.DropDownListHashTable.DataSource = null;

 16:  this.DropDownListHashTable.Items.Clear();

 17:  this.DropDownListHashTable.DataSource = objHashTable;

 18:  //* finding item is easier you just need to point to it by call its key

 19:  objHashTable.Remove("1002");

 20:  //*

 21:  this.DropDownListHashTable.DataTextField = "Value";

 22:  this.DropDownListHashTable.DataValueField = "Key";

 23:  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

 1: //Stack is LIFO: Last in First Out

 2:  System.Collections.Stack objStackPush = new System.Collections.Stack();

 3:  

 4:  //By Push method you can insert item at the top of the stack

 5:  objStackPush.Push("Mahsa");

 6:  objStackPush.Push("Hassankashi");

 7:  this.lblPop.Text = "";

 8:  this.ListBoxStack.DataSource = objStackPush.ToArray();

 9:  this.ListBoxStack.DataBind();

Pop操作

 1: System.Collections.Stack objStackPop = new System.Collections.Stack();

 2:  

 3: objStackPop.Push("Mahsa");

 4: objStackPop.Push("Hassankashi");

 5:  

 6: //By Pop method you can remove item from the top of the stack --> Last in First in

 7: this.lblPop.Text = objStackPop.Pop().ToString();

 8:  

 9: this.ListBoxStack.DataSource = objStackPop.ToArray();

 10: 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

 1: //Queue is FIFO: First in First Out

 2: System.Collections.Queue objQueue = new System.Collections.Queue();

 3:  

 4: //By Enqueue method you can insert item at the END of the Queue

 5: objQueue.Enqueue("Mahsa");

 6: objQueue.Enqueue("Hassankashi");

 7: objQueue.Enqueue("Cosmic");

 8: objQueue.Enqueue("Verse");

 9:  

 10: this.lblQueue.Text = "";

 11: this.ListBoxQueue.DataSource = objQueue.ToArray();

 12: 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();

List

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;

Stack Generic

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,>

来源：oschina

链接：https://my.oschina.net/u/1789896/blog/526881