C#中如何使用Join与GroupJoin将两个集合进行关联与分组
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对于Join的用法说明如下:
语法:
public static IEnumerableJoin ( this IEnumerable outer, IEnumerable inner, Func outerKeySelector, Func innerKeySelector, Func resultSelector )
参数说明:
outer Type: System.Collections.Generic.IEnumerable要联接的第一个序列。 inner Type: System.Collections.Generic.IEnumerable 要与第一个序列联接的序列。 outerKeySelector Type: System.Func 用于从第一个序列的每个元素提取联接键的函数。 innerKeySelector Type: System.Func 用于从第二个序列的每个元素提取联接键的函数。 resultSelector Type: System.Func 用于从两个匹配元素创建结果元素的函数。 返回值 Type: System.Collections.Generic.IEnumerable IEnumerable ,其类型的元素 TResult 通过对两个序列执行内部联接获得的。
参数类型:
TOuter 第一个序列中的元素的类型。 TInner 第二个序列中的元素的类型。 TKey 键选择器函数返回的键的类型。 TResult 结果元素的类型。
参考链接如下:
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 }; ListpList = new List { 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 dList = new List { 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}"; } } }
输出结果:
对于GroupJoin的用法说明如下:
语法:
public static IEnumerableGroupJoin ( this IEnumerable outer, IEnumerable inner, Func outerKeySelector, Func innerKeySelector, Func , TResult> resultSelector )
参数说明:
outer Type: System.Collections.Generic.IEnumerable
要联接的第一个序列。
inner Type: System.Collections.Generic.IEnumerable
要与第一个序列联接的序列。
outerKeySelector Type: System.Func
用于从第一个序列的每个元素提取联接键的函数。
innerKeySelector Type: System.Func
用于从第二个序列的每个元素提取联接键的函数。
resultSelector Type: System.Func, TResult>
用于从第一个序列的元素和第二个序列的匹配元素集合中创建结果元素的函数。
返回值
Type: System.Collections.Generic.IEnumerableIEnumerable ,其中包含类型的元素 TResult 通过对两个序列执行分组的联接获得的。
参数类型:
TOuter 第一个序列中的元素的类型。 TInner 第二个序列中的元素的类型。 TKey 键选择器函数返回的键的类型。 TResult 结果元素的类型。
参考链接如下:
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 }; ListpList = new List { 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 dList = new List { 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}"; } } }
输出结果:
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文章标题:C#中如何使用Join与GroupJoin将两个集合进行关联与分组
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