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", "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