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

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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 + "<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


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