LINQ (Language Integrated Query)

🔷 C# Programming Lesson 13 Advanced

LINQ (Language Integrated Query) is a powerful C# feature that allows you to query collections using a SQL-like syntax directly in your C# code.

1 Query Syntax vs. Method Syntax

LINQ queries can be written in two ways:

Query Syntax: Reads like SQL, starting with `from` and ending with `select`.
Method Syntax: Uses extension methods and lambda expressions (`Where`, `Select`, `OrderBy`), which is more common and powerful in modern C#.

2 LINQ Code

Let's run a program filtering and sorting list collections using LINQ expressions:

C# — LINQ Queries ▶ Run Code

using System;
using System.Collections.Generic;
using System.Linq; // Required for LINQ extension methods

class Program {
    static void Main() {
        List<int> numbers = new List<int>() { 1, 4, 8, 12, 15, 20 };

        // Filter numbers greater than 10 (using Method Syntax)
        var filtered = numbers.Where(n => n > 10).ToList();
        
        Console.Write("Numbers > 10: ");
        foreach (var num in filtered) {
            Console.Write(num + " ");
        }
        Console.WriteLine();

        // Sort names alphabetically
        List<string> names = new List<string>() { "Charlie", "Alice", "Bob" };
        var sortedNames = names.OrderBy(name => name).ToList();
        
        Console.WriteLine("Sorted Names: " + string.Join(", ", sortedNames));
    }
}

3 Code Challenge

Challenge: Write a LINQ query that filters an array of test scores, returning only scores that are 80 or above, sorted in descending order. Output the filtered scores.