步步为营VS 2008 + .NET 3.5(6) - LINQ查询操作符之Distinct、Union、Concat、Intersect、Except

[索引页]
[源码下载]


[align=center]步步为营VS 2008 + .NET 3.5(6) - LINQ查询操作符之Distinct、Union、Concat、Intersect、Except、Skip、Take、SkipWhile、TakeWhile、Single、SingleOrDefault、Reverse、SelectMany[/align]

作者：webabcd

介绍
·Distinct - 过滤集合中的相同项；延迟
·Union - 连接不同集合，自动过滤相同项；延迟
·Concat - 连接不同集合，不会自动过滤相同项；延迟
·Intersect - 获取不同集合的相同项（交集）；延迟
·Except - 从某集合中删除其与另一个集合中相同的项；延迟
·Skip - 跳过集合的前n个元素；延迟
·Take - 获取集合的前n个元素；延迟
·SkipWhile - 直到某一条件成立就停止跳过；延迟
·TakeWhile - 直到某一条件成立就停止获取；延迟
·Single - 根据表达式返回集合中的某一元素；不延迟
·SingleOrDefault - 根据表达式返回集合中的某一元素（如果没有则返回默认值）；不延迟
·Reverse - 对集合反向排序；延迟
·SelectMany - Select选择（一对多）；延迟

示例
Summary2.aspx.cs


using System;


using System.Data;


using System.Configuration;


using System.Collections;


using System.Linq;


using System.Web;


using System.Web.Security;


using System.Web.UI;


using System.Web.UI.WebControls;


using System.Web.UI.WebControls.WebParts;


using System.Web.UI.HtmlControls;


using System.Xml.Linq;




using System.Collections.Generic;


using DAL;




public partial class LINQ_Summary2 : System.Web.UI.Page


{


NorthwindDataContext _ctx = new NorthwindDataContext();


string[] _ary = null;




protected void Page_Load(object sender, EventArgs e)


{


_ary = new string[] { "asp.net", "csharp", "xhtml", "css", "javascript", "wcf", "wpf",


"asp.net", "csharp", "xhtml", "css", "javascript",


"silverlight", "linq", "wf", "sqlserver", "asp.net ajax", "ssis", "ssas", "ssrs" };




// Distinct - 过滤集合中的相同项；延迟


Summary_Distinct();




// Union - 连接不同集合，自动过滤相同项；延迟


Summary_Union();




// Concat - 连接不同集合，不会自动过滤相同项；延迟


Summary_Concat();




// Intersect - 获取不同集合的相同项（交集）；延迟


Summary_Intersect();




// Except - 从某集合中删除其与另一个集合中相同的项；延迟


Summary_Except();




// Skip - 跳过集合的前n个元素；延迟


// Take - 获取集合的前n个元素；延迟


Summary_Skip_Take();




// SkipWhile - 直到某一条件成立就停止跳过；延迟


// TakeWhile - 直到某一条件成立就停止获取；延迟


Summary_SkipWhile_TakeWhile();




// Single - 根据表达式返回集合中的某一元素；不延迟


// SingleOrDefault - 根据表达式返回集合中的某一元素（如果没有则返回默认值）；不延迟


Summary_Single_SingleOrDefault();




// Reverse - 对集合反向排序；延迟


Summary_Reverse();




// SelectMany - Select选择（一对多）；延迟


Summary_SelectMany();


}


}

Distinct - 过滤集合中的相同项；延迟

/// <summary>


/// Distinct - 过滤集合中的相同项；延迟


/// </summary>


void Summary_Distinct()


{


var ary = (from a in _ary


select a).Distinct();




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
asp.net
csharp
xhtml
css
javascript
wcf
wpf
silverlight
linq
wf
sqlserver
asp.net ajax
ssis
ssas
ssrs

Union - 连接不同集合，自动过滤相同项；延迟

/// <summary>


/// Union - 连接不同集合，自动过滤相同项；延迟


/// </summary>


void Summary_Union()


{


var ary = (from a in _ary


select a).Take(3).Union((from a in _ary


select a).Take(6));




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
asp.net
csharp
xhtml
css
javascript
wcf

Concat - 连接不同集合，不会自动过滤相同项；延迟

/// <summary>


/// Concat - 连接不同集合，不会自动过滤相同项；延迟


/// </summary>


void Summary_Concat()


{


var ary = (from a in _ary


select a).Take(3).Concat((from a in _ary


select a).Take(6));




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
asp.net
csharp
xhtml
asp.net
csharp
xhtml
css
javascript
wcf

Intersect - 获取不同集合的相同项（交集）；延迟


/// <summary>


/// Intersect - 获取不同集合的相同项（交集）；延迟


/// </summary>


void Summary_Intersect()


{


var ary = (from a in _ary


select a).Take(3).Intersect((from a in _ary


select a).Skip(1).Take(3));




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
csharp
xhtml

Except - 从某集合中删除其与另一个集合中相同的项；延迟

/// <summary>


/// Except - 从某集合中删除其与另一个集合中相同的项；延迟


/// </summary>


void Summary_Except()


{


var ary = (from a in _ary


select a).Take(3).Except((from a in _ary


select a).Skip(1).Take(3));




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
asp.net

Skip - 跳过集合的前n个元素；延迟
Take - 获取集合的前n个元素；延迟


/// <summary>


/// Skip - 跳过集合的前n个元素；延迟


/// Take - 获取集合的前n个元素；延迟


/// </summary>


void Summary_Skip_Take()


{


var ary = (from a in _ary


select a).Skip(2).Take(3);




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
xhtml
css
javascript

SkipWhile - 直到某一条件成立就停止跳过；延迟
TakeWhile - 直到某一条件成立就停止获取；延迟

/// <summary>


/// SkipWhile - 直到某一条件成立就停止跳过；延迟


/// TakeWhile - 直到某一条件成立就停止获取；延迟


/// </summary>


void Summary_SkipWhile_TakeWhile()


{


var ary = (from a in _ary


select a).SkipWhile(s => s.Length < 8).TakeWhile(s => s.Length > 2);




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
javascript
wcf
wpf
asp.net
csharp
xhtml
css
javascript
silverlight
linq

Single - 根据表达式返回集合中的某一元素；不延迟
SingleOrDefault - 根据表达式返回集合中的某一元素（如果没有则返回默认值）；不延迟


/// <summary>


/// Single - 根据表达式返回集合中的某一元素；不延迟


/// SingleOrDefault - 根据表达式返回集合中的某一元素（如果没有则返回默认值）；不延迟


/// </summary>


void Summary_Single_SingleOrDefault()


{


string s = (from a in _ary


select a).Single(a => a == "silverlight");


// string s = (from a in _ary


// select a).SingleOrDefault(a => a == "xxx");


// s == null




result.InnerHtml += s + "<br />";


result.InnerHtml += "<br />";


}

运行结果
silverlight

Reverse - 对集合反向排序；延迟


/// <summary>


/// Reverse - 对集合反向排序；延迟


/// </summary>


void Summary_Reverse()


{


var ary = (from a in _ary


orderby a.Length ascending


select a).Reverse();




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
asp.net ajax
silverlight
javascript
javascript
sqlserver
asp.net
asp.net
csharp
csharp
xhtml
xhtml
ssrs
ssas
ssis
linq
css
wpf
wcf
css
wf

SelectMany - Select选择（一对多）；延迟

/// <summary>


/// SelectMany - Select选择（一对多）；延迟


/// </summary>


void Summary_SelectMany()


{


var ary = (from a in _ary


where a.Contains(".")


select a).SelectMany(a => a.Split('.'));




foreach (string s in ary)


{


result.InnerHtml += s + "<br />";


}


result.InnerHtml += "<br />";


}

运行结果
asp
net
asp
net
asp
net ajax

OK
[源码下载]