LINQ GroupBy() Method

In LINQ, the GroupBy operator is used to groupin the list/collection items based on the specified value of the key, and it returns a collection of IGrouping<key, Values>. The GroupBy method in LINQ is the same as the SQL group by statement.

Syntax of LINQ GroupBy() Method

Here is the syntax of using the LINQ GroupBy() method to group the elements based on the specified value of the key.

From the above syntax, we are grouping the "objStudent" items of the collection based on the student location.

Example of LINQ GroupBy() in Method Syntax

Here is the example of using the LINQ GroupBy() in method syntax.

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; }
    }
    }

In the above example, we are grouping the collection of items in "objStudent" based on the location of the student.

Output:

Example of LINQ GroupBy() in Query Syntax

Here is the example of using the LINQ GroupBy() operator.

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; }
    }
    }

Output: