C#中使用Join與GroupJoin將兩個集合進(jìn)行關(guān)聯(lián)與分組

更新時間：2017年12月05日 14:14:36 作者：cnc

這篇文章主要介紹了C#中使用Join與GroupJoin將兩個集合進(jìn)行關(guān)聯(lián)與分組,文中分別對Join和GroupJoin的用法進(jìn)行詳細(xì)說明,需要的朋友可以參考下

本文使用的開發(fā)環(huán)境是VS2017及dotNet4.0，寫此隨筆的目的是給自己及新開發(fā)人員作為參考，

對于Join的用法說明如下：

語法：

public static IEnumerable<TResult> Join<TOuter, TInner, TKey, TResult>(
 this IEnumerable<TOuter> outer,
 IEnumerable<TInner> inner,
 Func<TOuter, TKey> outerKeySelector,
 Func<TInner, TKey> innerKeySelector,
 Func<TOuter, TInner, TResult> resultSelector
)

參數(shù)說明：

outer
Type: System.Collections.Generic.IEnumerable<TOuter>
要聯(lián)接的第一個序列。
inner
Type: System.Collections.Generic.IEnumerable<TInner>
要與第一個序列聯(lián)接的序列。
outerKeySelector
Type: System.Func<TOuter, TKey>
用于從第一個序列的每個元素提取聯(lián)接鍵的函數(shù)。
innerKeySelector
Type: System.Func<TInner, TKey>
用于從第二個序列的每個元素提取聯(lián)接鍵的函數(shù)。
resultSelector
Type: System.Func<TOuter, TInner, TResult>
用于從兩個匹配元素創(chuàng)建結(jié)果元素的函數(shù)。
返回值
Type: System.Collections.Generic.IEnumerable<TResult>
IEnumerable<T> ，其類型的元素 TResult 通過對兩個序列執(zhí)行內(nèi)部聯(lián)接獲得的。

參數(shù)類型：

TOuter
第一個序列中的元素的類型。
TInner
第二個序列中的元素的類型。
TKey
鍵選擇器函數(shù)返回的鍵的類型。
TResult
結(jié)果元素的類型。

參考鏈接如下：

https://msdn.microsoft.com/zh-cn/library/bb534675.aspx
https://docs.microsoft.com/zh-cn/dotnet/api/system.linq.enumerable.join?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DZH-CN%26k%3Dk(System.Linq.Enumerable.Join%60%604);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.0);k(DevLang-csharp)%26rd%3Dtrue&view=netframework-4.7.1

例程：

using System;
using System.Collections.Generic;
using System.Linq;
namespace ConsoleApp33
{
 class Program
 {
 static void Main(string[] args)
 {
  GroupJoinEx();
 }
 static void GroupJoinEx()
 {
  Person p1 = new Person() { Name = "ABC", Age = 18 };
  Person p2 = new Person() { Name = "EFG", Age = 19 };
  Person p3 = new Person() { Name = "LMN", Age = 20 };
  Person p4 = new Person() { Name = "XYZ", Age = 21 };
  List<Person> pList = new List<Person> { p1, p2, p3, p4 };
  Department d1 = new Department() { Name = "A1", Employee = p1 };
  Department d2 = new Department() { Name = "A2", Employee = p2 };
  Department d3 = new Department() { Name = "A3", Employee = p1 };
  Department d4 = new Department() { Name = "B1", Employee = p3 };
  Department d5 = new Department() { Name = "B2", Employee = p4 };
  Department d6 = new Department() { Name = "B3", Employee = p4 };
  List<Department> dList = new List<Department> { d1, d2, d3, d4, d5, d6 };
  var result = pList.Join(dList,
  person => person,
  department => department.Employee,
  (person, department) => new
  {
   Person = person,
   Department = department
  });
  foreach(var item1 in result)
  {
  Console.Write($"Name:{item1.Person} & Department:{item1.Department} ");
  Console.WriteLine();
  }
 }
 }
 class Person
 {
 public string Name { set; get; }
 public int Age { set; get; }
 public override string ToString()
 {
  return $"{Name},{Age}";
 }
 }
 class Department
 {
 public string Name { set; get; }
 public Person Employee { set; get; }
 public override string ToString()
 {
  return $"{Name}";
 }
 }
}

輸出結(jié)果：

對于GroupJoin的用法說明如下：

語法：

public static IEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult>(
 this IEnumerable<TOuter> outer,
 IEnumerable<TInner> inner,
 Func<TOuter, TKey> outerKeySelector,
 Func<TInner, TKey> innerKeySelector,
 Func<TOuter, IEnumerable<TInner>, TResult> resultSelector
)

參數(shù)說明：

outer
Type: System.Collections.Generic.IEnumerable<TOuter>

要聯(lián)接的第一個序列。

inner
Type: System.Collections.Generic.IEnumerable<TInner>

要與第一個序列聯(lián)接的序列。

outerKeySelector
Type: System.Func<TOuter, TKey>

用于從第一個序列的每個元素提取聯(lián)接鍵的函數(shù)。

innerKeySelector
Type: System.Func<TInner, TKey>

用于從第二個序列的每個元素提取聯(lián)接鍵的函數(shù)。

resultSelector
Type: System.Func<TOuter, IEnumerable<TInner>, TResult>

用于從第一個序列的元素和第二個序列的匹配元素集合中創(chuàng)建結(jié)果元素的函數(shù)。

返回值

Type: System.Collections.Generic.IEnumerable<TResult>
IEnumerable<T> ，其中包含類型的元素 TResult 通過對兩個序列執(zhí)行分組的聯(lián)接獲得的。

參數(shù)類型：

TOuter
第一個序列中的元素的類型。
TInner
第二個序列中的元素的類型。
TKey
鍵選擇器函數(shù)返回的鍵的類型。
TResult
結(jié)果元素的類型。

參考鏈接如下：

https://msdn.microsoft.com/zh-cn/library/bb534297.aspx
https://docs.microsoft.com/zh-cn/dotnet/api/system.linq.enumerable.groupjoin?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DZH-CN%26k%3Dk(System.Linq.Enumerable.GroupJoin%60%604);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.0);k(DevLang-csharp)%26rd%3Dtrue&view=netframework-4.7.1

例程：

using System;
using System.Collections.Generic;
using System.Linq;
namespace ConsoleApp33
{
 class Program
 {
 static void Main(string[] args)
 {
  GroupJoinEx();
 }
 static void GroupJoinEx()
 {
  Person p1 = new Person() { Name = "ABC", Age = 18 };
  Person p2 = new Person() { Name = "EFG", Age = 19 };
  Person p3 = new Person() { Name = "LMN", Age = 20 };
  Person p4 = new Person() { Name = "XYZ", Age = 21 };
  List<Person> pList = new List<Person> { p1, p2, p3, p4 };
  Department d1 = new Department() { Name = "A1", Employee = p1 };
  Department d2 = new Department() { Name = "A2", Employee = p2 };
  Department d3 = new Department() { Name = "A3", Employee = p1 };
  Department d4 = new Department() { Name = "B1", Employee = p3 };
  Department d5 = new Department() { Name = "B2", Employee = p4 };
  Department d6 = new Department() { Name = "B3", Employee = p4 };
  List<Department> dList = new List<Department> { d1, d2, d3, d4, d5, d6 };
  var result = pList.GroupJoin(dList,
  person => person,
  department => department.Employee,
  (person, departments) => new
  {
   Person = person,
   Department = departments.Select(d => d)
  });
  foreach(var item1 in result)
  {
  Console.Write($"Name:{item1.Person} & ");
  foreach(var item2 in item1.Department)
  {
   if(item1.Department.First() == item2)
   Console.Write($"Department:{item2} ");
   else
   Console.Write($"{item2} ");
  }
  Console.WriteLine();
  }
 }
 }
 class Person
 {
 public string Name { set; get; }
 public int Age { set; get; }
 public override string ToString()
 {
  return $"{Name},{Age}";
 }
 }
 class Department
 {
 public string Name { set; get; }
 public Person Employee { set; get; }
 public override string ToString()
 {
  return $"{Name}";
 }
 }
}

輸出結(jié)果：