How can I use LINQ to group queries in C#?

How can I use LINQ to group queries in C#?

You can use the GroupBy method in LINQ to group elements based on a key. For example, if you have a list of students and you want to group them by their grades, you can do it like this:

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

Can you show me a complete example with a list of objects?

Sure! Here's a complete example:

public class Student {
    public string Name { get; set; }
    public string Grade { get; set; }
}

var students = new List<Student> {
    new Student { Name = "Alice", Grade = "A" },
    new Student { Name = "Bob", Grade = "B" },
    new Student { Name = "Charlie", Grade = "A" }
};

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

foreach (var group in groupedStudents) {
    Console.WriteLine($"Grade: {group.Key}");
    foreach (var student in group) {
        Console.WriteLine($" - {student.Name}");
    }
}

What if I want to count the number of students in each group?

You can use the Select method to project the results into a new form. Here's how you can count the students in each group:

var studentCounts = students.GroupBy(s => s.Grade)
                             .Select(g => new { Grade = g.Key, Count = g.Count() });

foreach (var item in studentCounts) {
    Console.WriteLine($"Grade: {item.Grade}, Count: {item.Count}");
}