GroupBy in Linq

GroupBy in LINQ is used to group records that have the same value in a particular column or property.

Simple Example

Suppose you have a list of employees:

var employees = new List
{
    new Employee { Name = "John", Department = "IT" },
    new Employee { Name = "Mary", Department = "HR" },
    new Employee { Name = "David", Department = "IT" },
    new Employee { Name = "Sara", Department = "HR" }
};

Group By Department

var groupedEmployees = employees.GroupBy(e => e.Department);

Reading the Result

foreach (var group in groupedEmployees)
{
    Console.WriteLine($"Department: {group.Key}");

    foreach (var employee in group)
    {
        Console.WriteLine(employee.Name);
    }
}

GroupBy in LINQ is used to group a collection of items based on a key. It is similar to the SQL GROUP BY clause.

Syntax

var result = collection.GroupBy(x => x.Property);

Example 1: Group Employees by Department

var employees = new List

{

new Employee { Id = 1, Name = "John", Department = "IT" },

new Employee { Id = 2, Name = "David", Department = "HR" },

new Employee { Id = 3, Name = "Mike", Department = "IT" },

new Employee { Id = 4, Name = "Sara", Department = "HR" }

};

var groupedEmployees = employees.GroupBy(e => e.Department);

foreach (var group in groupedEmployees)

{

Console.WriteLine($"Department: {group.Key}");

foreach (var employee in group)

{

Console.WriteLine(employee.Name);

}

}

Output:

Department: IT

John

Mike

Department: HR

David

Sara

Example 2: Group and Count

var result = employees

.GroupBy(e => e.Department)

.Select(g => new

{

Department = g.Key,

EmployeeCount = g.Count()

});

foreach (var item in result)

{

Console.WriteLine($"{item.Department} - {item.EmployeeCount}");

}

Output:

IT - 2

HR - 2

Example 3: Multiple Columns Grouping

var result = employees.GroupBy(e => new

{

e.Department,

e.City

});

Equivalent SQL:

SELECT Department, City, COUNT(*)

FROM Employees

GROUP BY Department, City;

Query Syntax

var result =

from e in employees

group e by e.Department into grp

select new

{

Department = grp.Key,

Count = grp.Count()

};

Common Usage with Entity Framework

var warrantySummary = db.tbl_asset_warranty

.GroupBy(w => w.ClaimStatus)

.Select(g => new

{

ClaimStatus = g.Key,

TotalCount = g.Count()

})

.ToList();

This returns the count of warranties grouped by ClaimStatus.

Hi Yaad Dhakal,

GroupBy in LINQ is used to group elements that share a key.

Syntax

var grouped = items.GroupBy(x => x.KeyProperty);

It returns groups of type IGrouping.

Example

var students = new[]
{
    new { Name = "A", Grade = "A" },
    new { Name = "B", Grade = "B" },
    new { Name = "C", Grade = "A" }
};

var byGrade = students.GroupBy(s => s.Grade);

foreach (var group in byGrade)
{
    Console.WriteLine($"Grade: {group.Key}");

    foreach (var student in group)
        Console.WriteLine($"  {student.Name}");
}

Glad to help! Please mark this answer as the accepted answer if it helped you out!