Linq 集合操作

演示代码

两个对象一个是Person，一个Address, AddressId是外键，

public class Person

{

public string ID { get; set; }

public string Name { get; set; }

public int Age { get; set; }

public double Salary { get; set; }

public DateTime Born { get; set; }

public int IdAddress { get; set; }

}

public class Address

{

public int IdAddress { get; set; }

public string Street { get; set; }

public int Num { get; set; }

public string City { get; set; }

}

　　

测试数据如下

Person类

Address类

下面我会用7个方式实现7中集合操作

  1. INNER JOIN 内链接
  2. LEFT JOIN 左连接
  3. RIGHT JOIN 右链接
  4. FULL OUTER JOIN 所有
  5. LEFT JOIN EXCLUDING INNER JOIN 左空
  6. RIGHT JOIN EXCLUDING INNER JOIN 右空
  7. FULL OUTER JOIN EXCLUDING INNER JOIN ？？

    学校数学没学好不知道专业术语！哈哈

    INNER JOIN

    最常用的方法，两表关联查询

    标准Linq语法

    var result = from p in Person.BuiltPersons()

join a in Address.BuiltAddresses()

on p.IdAddress equals a.IdAddress

select new

     {

Name = a.MyPerson.Name,

Age = a.MyPerson.Age,

PersonIdAddress = a.MyPerson.IdAddress,

AddressIdAddress = a.MyAddress.IdAddress,

Street = a.MyAddress.Street

     };

    　　

    Lambda Expression:

    var resultJoint = Person.BuiltPersons().Join( /// Source Collection

Address.BuiltAddresses(), /// Inner Collection

p => p.IdAddress, /// PK

a => a.IdAddress, /// FK

(p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection

.Select(a => new

{

Name = a.MyPerson.Name,

Age = a.MyPerson.Age,

PersonIdAddress = a.MyPerson.IdAddress,

AddressIdAddress = a.MyAddress.IdAddress,

Street = a.MyAddress.Street

});

    　　

    Lambda表达式主要有5部分

  8. Is the main Collection. 
  9. Is the inner Collection.
  10. Is the PK.
  11. Is the FK.
  12. Is the type for the result collection. 

    查询结果如下

    LEFT JOIN

    新增一个LeftJoin的扩展方法

    public static IEnumerable<TResult>

    LeftJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,

IEnumerable<TInner> inner,

Func<TSource, TKey> pk,

Func<TInner, TKey> fk,

Func<TSource, TInner, TResult> result)

{

IEnumerable<TResult> _result = Enumerable.Empty<TResult>();

_result = from s in source

join i in inner

on pk(s) equals fk(i) into joinData

from left in joinData.DefaultIfEmpty()

select result(s, left);

return _result;

}

    　　

    Lambda Expression:

    var resultJoint = Person.BuiltPersons().LeftJoin( /// Source Collection

Address.BuiltAddresses(), /// Inner Collection

p => p.IdAddress, /// PK

a => a.IdAddress, /// FK

(p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection

.Select(a => new

{

Name = a.MyPerson.Name,

Age = a.MyPerson.Age,

PersonIdAddress = a.MyPerson.IdAddress,

AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),

            Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")

});

    　　

    注意：如果address为空Null需要做一个替换，否则会报错

    查询结果如下

    RIGHT JOIN

    Extension Method:

    public static IEnumerable<TResult>

    RightJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,

IEnumerable<TInner> inner,

Func<TSource, TKey> pk,

Func<TInner, TKey> fk,

Func<TSource, TInner, TResult> result)

{

IEnumerable<TResult> _result = Enumerable.Empty<TResult>();

_result = from i in inner

join s in source

on fk(i) equals pk(s) into joinData

from right in joinData.DefaultIfEmpty()

select result(right, i);

return _result;

}

    　　

    Lambda Expression:

    var resultJoint = Person.BuiltPersons().RightJoin( /// Source Collection

Address.BuiltAddresses(), /// Inner Collection

p => p.IdAddress, /// PK

a => a.IdAddress, /// FK

(p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection

.Select(a => new

{

Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),

Age = (a.MyPerson != null ? a.MyPerson.Age : -1),

PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),

AddressIdAddress = a.MyAddress.IdAddress,

Street = a.MyAddress.Street

});

    　　

    查询结果如下

    FULL OUTER JOIN

    Extension Method:

    public static IEnumerable<TResult>

    FullOuterJoinJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,

IEnumerable<TInner> inner,

Func<TSource, TKey> pk,

Func<TInner, TKey> fk,

Func<TSource, TInner, TResult> result)

{

var left = source.LeftJoin(inner, pk, fk, result).ToList();

var right = source.RightJoin(inner, pk, fk, result).ToList();

return left.Union(right);

}

    　　

    Lambda Expression:

    var resultJoint = Person.BuiltPersons().FullOuterJoinJoin( /// Source Collection

Address.BuiltAddresses(), /// Inner Collection

p => p.IdAddress, /// PK

a => a.IdAddress, /// FK

(p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection

.Select(a => new

{

Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),

Age = (a.MyPerson != null ? a.MyPerson.Age : -1),

PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),

AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),

Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")

});

    　　

    注意：每个对象都需要验证Null

    查询结果如下

    LEFT EXCLUDING JOIN

    Extension Method:

    public static IEnumerable<TResult>

    LeftExcludingJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,

IEnumerable<TInner> inner,

Func<TSource, TKey> pk,

Func<TInner, TKey> fk,

Func<TSource, TInner, TResult> result)

{

IEnumerable<TResult> _result = Enumerable.Empty<TResult>();

_result = from s in source

join i in inner

on pk(s) equals fk(i) into joinData

from left in joinData.DefaultIfEmpty()

where left == null

select result(s, left);

return _result;

}

    　　

    Lambda Expression:

    var resultJoint = Person.BuiltPersons().LeftExcludingJoin( /// Source Collection

Address.BuiltAddresses(), /// Inner Collection

p => p.IdAddress, /// PK

a => a.IdAddress, /// FK

(p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection

.Select(a => new

{

Name = a.MyPerson.Name,

Age = a.MyPerson.Age,

PersonIdAddress = a.MyPerson.IdAddress,

AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),

Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")

});

    　　

    查询结果如下

    RIGHT EXCLUDING JOIN

    Extension Method:

    public static IEnumerable<TResult>

RightExcludingJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,

IEnumerable<TInner> inner,

Func<TSource, TKey> pk,

Func<TInner, TKey> fk,

Func<TSource, TInner, TResult> result)

{

IEnumerable<TResult> _result = Enumerable.Empty<TResult>();

_result = from i in inner

join s in source

on fk(i) equals pk(s) into joinData

from right in joinData.DefaultIfEmpty()

where right == null

select result(right, i);

return _result;

}

    　　

    Lambda Expression:

    var resultJoint = Person.BuiltPersons().RightExcludingJoin( /// Source Collection

Address.BuiltAddresses(), /// Inner Collection

p => p.IdAddress, /// PK

a => a.IdAddress, /// FK

(p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection

.Select(a => new

{

Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),

Age = (a.MyPerson != null ? a.MyPerson.Age : -1),

PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),

AddressIdAddress = a.MyAddress.IdAddress,

Street = a.MyAddress.Street

});

    　　

    查询结果

    FULL OUTER EXCLUDING JOIN

    Extension Method:

    public static IEnumerable<TResult>

FulltExcludingJoin<TSource, TInner, TKey, TResult>(this IEnumerable<TSource> source,

IEnumerable<TInner> inner,

Func<TSource, TKey> pk,

Func<TInner, TKey> fk,

Func<TSource, TInner, TResult> result)

{

var left = source.LeftExcludingJoin(inner, pk, fk, result).ToList();

var right = source.RightExcludingJoin(inner, pk, fk, result).ToList();

return left.Union(right);

}

    　　

    Lambda Expression:

    var resultJoint = Person.BuiltPersons().FulltExcludingJoin( /// Source Collection

Address.BuiltAddresses(), /// Inner Collection

p => p.IdAddress, /// PK

a => a.IdAddress, /// FK

(p, a) => new { MyPerson = p, MyAddress = a }) /// Result Collection

.Select(a => new

{

Name = (a.MyPerson != null ? a.MyPerson.Name : "Null-Value"),

Age = (a.MyPerson != null ? a.MyPerson.Age : -1),

PersonIdAddress = (a.MyPerson != null ? a.MyPerson.IdAddress : -1),

AddressIdAddress = (a.MyAddress != null ? a.MyAddress.IdAddress : -1),

Street = (a.MyAddress != null ? a.MyAddress.Street : "Null-Value")

});

    　　

    查询结果

Linq 集合操作的更多相关文章

  1. Linq集合操作之Intersect,Except,Union源码分析

    Linq集合操作之Intersect,Except,Union源码分析 linq的集合运算 常见的集合运算有哪些? 这三个扩展方法在我们实际使用中用的还是非常多的,而且这里还涉及到了“复杂度” 无算法 ...

  2. C#LINQ集合操作

    LINQ的集合运算 List<int> lstOne = new List<int>() { 1, 55, 223, 25 }; List<int> lstTwo ...

  3. Linq聚合操作之Aggregate,Count,Sum,Distinct源码分析

    Linq聚合操作之Aggregate,Count,Sum,Distinct源码分析 一:Linq的聚合运算 1. 常见的聚合运算:Aggregate,Count, Sum, Distinct,Max, ...

  4. Linq生成操作之DefautIfEmpty,Empty,Range,Repeat源码分析

    Linq生成操作之DefautIfEmpty,Empty,Range,Repeat源码分析 Linq的四种生成运算 DefautIfEmpty,Empty,Range,Repeat 也就是给我们初始化 ...

  5. Linq转换操作之OfType,Cast,AsEnumerable,ToLookup源码分析

    Linq转换操作之OfType,Cast,AsEnumerable,ToLookup源码分析 一:Tolookup 1. 从方法的注解上可以看到,ToLookup也是一个k,v的形式,那么问题来了,它 ...

  6. Linq转换操作之ToArray,ToList,ToDictionary源码分析

    Linq转换操作之ToArray,ToList,ToDictionary源码分析 一:linq中的转换运算符 1. ToArray 我们经常用在linq查询上吧. linq只能运用在IEnumerab ...

  7. 函数式Android编程（II）：Kotlin语言的集合操作

    原文标题:Functional Android (II): Collection operations in Kotlin 原文链接:http://antonioleiva.com/collectio ...

  8. JAVASE02-Unit05： 集合操作 —— 查找表

    Unit05: 集合操作 -- 查找表 使用该类测试自定义元素的集合排序 package day05; /** * 使用该类测试自定义元素的集合排序 * @author adminitartor * ...

  9. JAVASE02-Unit04： 集合框架 、 集合操作 —— 线性表

    Unit04: 集合框架 . 集合操作 -- 线性表 操作集合元素相关方法 package day04; import java.util.ArrayList; import java.util.Co ...

随机推荐

  1. JS中的事件大全

    一般事件  onClick            鼠标点击事件,多用在某个对象控制的范围内的鼠标点击 onDblClick        鼠标双击事件 onMouseDown        鼠标上的按 ...

  2. Keil STM32调试，使用ST-Link下载程序时提示“flash timeout.reset the target and try it again”

    参考: 很郁闷,买来没多久的 STM32F4-DISCOVERY 就挂了? STM32F103RB   Jlink调试的时候出现flash timeout.reset the target and t ...

  3. 一个苹果证书怎么多次使用——导出p12文件

    http://blog.csdn.net/jjiss318/article/details/41812243 原文:http://my.oschina.net/u/1245365/blog/19636 ...

  4. iOS 发布流程

    1.登陆苹果开发者中心http://developer.apple.com(99美元账号) 2.进入itunes connect 3.选择Manage Your Apps 4.选择Add New Ap ...

  5. JQuery中 json 和字符串直接相互转换

    json字符串转json对象:jQuery.parseJSON(jsonStr); json对象转json字符串:JSON.stringify(jsonObj);   IE中可能对unicode使用“ ...

  6. UVa 10299 - Relatives

    题目大意:Euler's Totient的应用. 几乎和UVa 10179 - Irreducable Basic Fractions一样,于是偷了个懒,直接用10179题的代码,结果WA了,感觉一样 ...

  7. List<KeyValuePair<TKey,TValue>> 与 Dictionary<TKey,TValue> 不同

    两者都可以通过 KeyValuePair<TKey,TValue> 进行遍历,并且两者可以相互转换: List<KeyValuePair<string,string>&g ...

  8. Visual Studio 2012 开发环境配置+控制台工具+桌面应用程序

    一.界面布局视图设置 1.窗口的布局.控制台窗口运行恢复到开发环境的设置方法 也可以保存好设好的个性化设置,导入设置: 2.视图|服务器资源管理器(sever explorer) 可以访问数据源.服务 ...

  9. IM 融云 之 安装cocoapods 安装 SDK

    1. podfile 内容如下: platform :ios, '7.0' pod 'RongCloudIMKitWithVoip', '2.4.3' 现在最新是2.4.3 导入之后,就直接可以用了. ...

  10. Python关键字yield的解释

    yield 是一个类似 return 的关键字,只是这个函数返回的是个生成器. >>> def createGenerator() : ... mylist = range(3) . ...