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 - webabcd - 专注于asp.net

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

Posted on 2007-10-16 08:17 webabcd 阅读(4555) 评论(18) 编辑收藏所属分类: LINQ&DLINQ&XLINQ

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

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

result.InnerHtml += " ";

}

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 + " ";

}

result.InnerHtml += " ";

}

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 + " ";

}