c# LINQ查询操作符实例操作总结2

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

[csharp]
view plaincopyprint?

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();
}
}

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

[csharp]
view plaincopyprint?

/// <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 />";
}

/// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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

[csharp]
view plaincopyprint?

/**//// <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 />";
}

/**//// <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