LINQ GroupBy()用法及代碼示例

在 LINQ 中，GroupBy 運算符用於根據鍵的指定值對列表/集合項進行分組，並返回 IGrouping<key, Values> 的集合。 LINQ 中的 GroupBy 方法與 SQL group by 語句相同。

LINQ GroupBy() 方法的語法

下麵是使用 LINQ GroupBy() 方法根據鍵的指定值對元素進行分組的語法。

var student1 = objStudent.GroupBy(x => x.Location);

根據上述語法，我們根據學生位置對集合的 "objStudent" 項進行分組。

方法語法中的 LINQ GroupBy() 示例

這是在方法語法中使用 LINQ GroupBy() 的示例。

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Programme2
    {
        static void Main(string[] args)
        {
//Create an object 'objStudent' of the list of the student
            List<Student> objStudent = new List<Student>
    ()
    {
    new Student() { Name = "Ak Tyagi", Gender = "Male",Location="Chennai" },
    new Student() { Name = "Rohini", Gender = "Female", Location="Chennai" },
    new Student() { Name = "Praveen", Gender = "Male",Location="Bangalore" },
    new Student() { Name = "Sateesh", Gender = "Male", Location ="Vizag"},
    new Student() { Name = "Madhav", Gender = "Male", Location="Nagpur"}
    };
   // here with the help of GrouBy we will fetch the student on the base of location
    var student1 = objStudent.GroupBy(x => x.Location);
    foreach (var sitem in student1)
    {
   // WriteLine() function here count the number of student
    Console.WriteLine(sitem.Key, sitem.Count());
    Console.WriteLine();
    foreach (var stud in sitem)
    {
    //Console.WriteLine(stud.Name + "\t" + stud.Location) show the information of the student on the base of the location
    Console.WriteLine(stud.Name + "\t" + stud.Location);
    }

    Console.WriteLine();

    }
    Console.ReadLine();
    }
    }
    //Student class containing the name of the student,gender and location of the student
    class Student
    {
    public string Name { get; set; }
    public string Gender { get; set; }
    public string Location { get; set; }
    }
    }

在上麵的例子中，我們根據學生的位置對 "objStudent" 中的項目集合進行分組。

輸出：

查詢語法中的 LINQ GroupBy() 示例

這是使用 LINQ GroupBy() 運算符的示例。

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApp1
{
    class Programme2
    {
        static void Main(string[] args)
        {
//create an object objStudent of the Student List and add some information
            List<Student> objStudent = new List<Student>
    ()
    {
    new Student() { Name = "Vinay Tyagi", Gender = "Male",Location="Chennai" },
    new Student() { Name = "Rohini", Gender = "Female", Location="Chennai" },
    new Student() { Name = "Praveen", Gender = "Male",Location="Bangalore" },
    new Student() { Name = "Sateesh Alavala", Gender = "Male", Location ="Vizag"},
    new Student() { Name = "Madhav Sai", Gender = "Male", Location="Nagpur"}
    };
    //apply the linq queries to group the information of the student according to the location
    /*linq queries starts from, from take a variable 'std' in 
        objStudent(object of the Student List) group 'std'(declared variable) by std.Location*/
    var student = from std in objStudent
    group std by std.Location;
    //foreach loop iterate over all the information of the student
    foreach (var sitem in student)
    {
    Console.WriteLine(sitem.Key, sitem.Count());
    Console.WriteLine();
    foreach (var stud in sitem)
    {
    /*Console.WriteLine(stud.Name + "\t" + stud.Location) show the 
    information of the student on the base of the location*/
    Console.WriteLine(stud.Name + "\t" + stud.Location);
    }
    Console.WriteLine();
    }
    Console.ReadLine();
    }
    }
    class Student
    {
    public string Name { get; set; }
    public string Gender { get; set; }
    public string Location { get; set; }
    }
    }

輸出：

相關用法

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