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. 改变Button文字和图片的位置

    button.imageEdgeInsets = UIEdgeInsetsMake(0, labelWidth, 0, -labelWidth);button.titleEdgeInsets = UI ...

  2. coreGraphs和动画

    http://www.jianshu.com/p/b71c3d450e8e http://blog.csdn.net/volcan1987/article/details/9969455 http:/ ...

  3. HUST 1601 Shepherd

    间隔小的时候dp预处理,大的时候暴力..正确做法不会... dp[i][j]表示以i为开头,间隔为j的和,递推:dp[i][j] = dp[i + j][j] + a[i] 测试数据中间隔可能是0.. ...

  4. 使用idea建立gradle+SSM项目

    目录: 一.创建一个gradle项目   二 .在gradle中创建SSM项目 一 .创建一个gradle项目 第一步: 第二步:选择gradle,并选中web,然后点击Next进入下一步 第三步:此 ...

  5. Xcode各版本官方下载

    官方下载, 用开发者账户登录,建议用Safari浏览器下载. 官方下载地址: https://developer.apple.com/xcode/downloads/ Xcode 66.4: http ...

  6. 查看错误日志发现有两个警告（ignored in --skip-name-resolve mode）

    2016-08-02 17:30:26 17374 [Warning] 'user' entry '@losnau-223.com' ignored in --skip-name-resolve mo ...

  7. JQuery的 jQuery.fn.extend() 和jQuery.extend();

    原文链接:http://caibaojian.com/jquery-extend-and-jquery-fn-extend.html jQuery.fn.extend(); jQuery.extend ...

  8. numpy 安装

    sudo apt-get install python-scipy sudo apt-get install python-numpy sudo apt-get install python-matp ...

  9. python查询mysql中文乱码问题

    python2.7 查询或者插入中文数据在mysql中的时候出现中文乱码 --- 可能情况: 1.mysql数据库各项没有设置编码,默认为'latin' 2.使用MySQL.connect的时候没有设 ...

  10. STM8S003/005/007芯片解密单片机解密程序提取复制经验分享！

    STM8S003/005/007芯片解密单片机解密程序提取复制 芯片解密型号: STM8S003K3T6,STM8S005K6T6,STM8S007C8T6,STM8S003F3P6 STM8S005 ...