VS 2008 + .NET 3.5 - LINQ查询操作符(二)

VS 2008 + .NET 3.5 - LINQ查询操作符(二)

VS 2008 + .NET 3.5 - LINQ查询操作符之distinct、Union、Concat、Intersect、Except、Skip、Take、Skipwhile、TakeWhile、Single、SingleOrDefault、Reverse、SelectMany

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",
            "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 + " ";
 }
 result.InnerHtml += " ";
 }

运行结果aspnetaspnetaspnet ajax

VS 2008 + .NET 3.5 - LINQ查询操作符(二)

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