How is the usage of groupby in LINQ?
In LINQ, the GroupBy method is used to group elements in a sequence based on a specified key. It returns a sequence containing the grouped elements. The GroupBy method can take a key selector function to extract keys from the elements in the sequence. Here is the syntax for the GroupBy method:
public static IEnumerable<IGrouping<TKey, TSource>> GroupBy<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector
)
In the above syntax, the source represents the sequence to be grouped, and the keySelector is a function that returns a key for each element.
Here is an example demonstrating how to use the GroupBy method:
var students = new List<Student>()
{
new Student { Name = "John", Age = 20 },
new Student { Name = "Jane", Age = 19 },
new Student { Name = "Tom", Age = 20 },
new Student { Name = "Alice", Age = 19 },
new Student { Name = "Bob", Age = 21 }
};
var groupedStudents = students.GroupBy(s => s.Age);
foreach (var group in groupedStudents)
{
Console.WriteLine($"Age: {group.Key}");
foreach (var student in group)
{
Console.WriteLine($"Name: {student.Name}");
}
}
In the above example, we used the GroupBy method to group students based on their age. Then, within a foreach loop, we iterate through each group and print out the age along with the student’s name.
The output will be as follows:
Age: 20
Name: John
Name: Tom
Age: 19
Name: Jane
Name: Alice
Age: 21
Name: Bob
The Student class in the above example is defined as follows:
public class Student
{
public string Name { get; set; }
public int Age { get; set; }
}
Please note that the GroupBy method returns an IEnumerable
