C# Tutorial 10.2 :LINQ to Objects

 LINQ is a powerful feature in C# that allows you to query and manipulate data in a declarative and SQL-like syntax. LINQ to Objects specifically enables you to query in-memory collections like arrays, lists, and other IEnumerable<T> types.

Let's create a simple console application to demonstrate LINQ to Objects with step-by-step explanations.

Step 1: Create a new Console Application

Open Visual Studio and create a new Console Application. Name it as you wish.

Step 2: Define a Sample Data Collection

For this tutorial, let's create a simple class and a collection of objects:

class Person

{

    public string Name { get; set; }

    public int Age { get; set; }

}

class Program

{

    static void Main()

    {

        List<Person> people = new List<Person>

        {

            new Person { Name = "John", Age = 25 },

            new Person { Name = "Alice", Age = 30 },

            new Person { Name = "Bob", Age = 22 },

            new Person { Name = "Eva", Age = 28 },

            new Person { Name = "Charlie", Age = 35 }

        };

        // LINQ queries will be applied to this collection

    }

}

Step 3: Basic LINQ Queries

Now, let's start with some basic LINQ queries.

Filtering

var adults = from person in people
             where person.Age >= 18
             select person;
foreach (var adult in adults)
{
    Console.WriteLine($"{adult.Name} is an adult.");
}

Projection

var namesOnly = from person in people
                select person.Name;
foreach (var name in namesOnly)
{
    Console.WriteLine($"Name: {name}");
}

Step 4: Ordering and Aggregation

Ordering

var orderedByAge = from person in people
                   orderby person.Age
                   select person;
foreach (var person in orderedByAge)
{
    Console.WriteLine($"{person.Name} - {person.Age} years old");
}

Aggregation

int averageAge = people.Average(person => person.Age);
Console.WriteLine($"Average Age: {averageAge}");

Step 5: Advanced LINQ Queries

Grouping

var groupedByAge = from person in people
                   group person by person.Age;
foreach (var group in groupedByAge)
{
    Console.WriteLine($"People aged {group.Key}:");
    foreach (var person in group)
    {
        Console.WriteLine($"  {person.Name}");
    }
}

Joining

var departments = new List<string> { "HR", "IT", "Finance", "Marketing" };
var peopleWithDepartments = from person in people
                            join department in departments 
                            on person.Age % departments.Count
                            equals departments.IndexOf(department)
                            select new { person.Name, Department = department };
foreach (var person in peopleWithDepartments)
{
    Console.WriteLine($"{person.Name} works in {person.Department} department.");
}

Conclusion

This tutorial covers the basics of LINQ to Objects in C#. You can explore more advanced features and operations, such as Skip, Take, Any, All, etc., to further enhance your querying capabilities. LINQ is a versatile tool that can greatly simplify data manipulation in your C# applications.