Lesson 2: LINQ Method Syntax & Extension Methods

LINQ method syntax is the most common way to write LINQ queries in C#. It uses extension methods defined in System.Linq, making queries fluent and easy to chain.

Using Extension Methods

Most LINQ operations are extension methods on IEnumerable<T>. That means you can call them directly on collections like arrays, lists, and query results.

using System.Linq;

var words = new[] { "apple", "banana", "grape", "avocado" };

var startsWithA = words
    .Where(w => w.StartsWith("a"))
    .OrderBy(w => w.Length)
    .Select(w => w.ToUpper());

foreach (var fruit in startsWithA)
{
    Console.WriteLine(fruit);
}

Common Method Syntax Operators

These operators are the building blocks for most LINQ queries:

• Where — filter items.
• Select — project each item into a new form.
• OrderBy / OrderByDescending — sort results.
• GroupBy — group items by a key.
• Join — combine related collections.

Lambda Expressions

LINQ method syntax typically uses lambdas to define predicates and projections. Lambdas are small anonymous functions written with =>.

var prices = new List<decimal> { 12.50m, 7.99m, 19.95m, 3.49m };

var expensive = prices.Where(price => price > 10.00m);
var rounded = prices.Select(price => Math.Round(price));

Chaining Queries

The real power of method syntax is chaining multiple operators in a single expression.

var result = words
    .Where(w => w.Length > 5)
    .OrderByDescending(w => w)
    .Select(w => new { Text = w, Length = w.Length });

LINQ and In-Memory Collections

LINQ method syntax is perfect for filtering lists, arrays, dictionaries, and any sequence that implements IEnumerable<T>.

Lesson Summary