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：
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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：
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outerType: System.Collections.Generic.IEnumerable<TOuter>要聯(lián)接的第一個序列。innerType: System.Collections.Generic.IEnumerable<TInner>要與第一個序列聯(lián)接的序列。outerKeySelectorType: 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)。innerKeySelectorType: 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)。resultSelectorType: 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：
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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：
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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：
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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：
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outerType: System.Collections.Generic.IEnumerable<TOuter> |
要聯(lián)接的第一個序列。
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innerType: System.Collections.Generic.IEnumerable<TInner> |
要與第一個序列聯(lián)接的序列。
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outerKeySelectorType: 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)。
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innerKeySelectorType: 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)。
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resultSelectorType: 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
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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：
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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：
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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：
以上代碼僅在Join與GroupJoin最后一個參數(shù)有區(qū)別，可以參見紅色字體部分，
并從以上結(jié)果來看，Join與GroupJoin的區(qū)別一個在于：Join僅僅是將兩個結(jié)合進行關(guān)聯(lián)，而GroupJoin則會進行分組。
總結(jié)
以上所述是小編給大家介紹的C#中使用Join與GroupJoin將兩個集合進行關(guān)聯(lián)與分組，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復(fù)大家的。在此也非常感謝大家對服務(wù)器之家網(wǎng)站的支持！
原文鏈接：http://www.cnblogs.com/cncc/p/7985843.html
