LINQ Basics

Filter with Where

LINQ extends collections with query operators.

var nums = new List<int> { 1, 2, 3, 4, 5 };
var evens = nums.Where(n => n % 2 == 0);
Console.WriteLine(string.Join(",", evens));

Project with Select

Transform each element into a new shape.

var labels = nums.Select(n => $"#{n}");
foreach (var label in labels)
{
    Console.WriteLine(label);
}

Pick a single item

FirstOrDefault returns a default when nothing matches.

int firstBig = nums.FirstOrDefault(n => n > 3);
Console.WriteLine(firstBig);

LINQ habits

• Queries are lazy until you enumerate or call ToList
• Keep lambdas short and readable
• Prefer LINQ for clarity, not for every tiny loop
• Method syntax is common; query syntax also exists