Bits of .NET

🔍 LINQ = Query Collections

Loops are messy. LINQ queries collections cleanly. Filter, sort, group, aggregate — all in one.

📝 LINQ Methods

var numbers = new List { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

// Filter
var evens = numbers.Where(n => n % 2 == 0);
var evensList = evens.ToList(); // [2, 4, 6, 8, 10]

// Select (project)
var doubled = numbers.Select(n => n * 2).ToList();

// Filter and select
var squaredEvens = numbers
    .Where(n => n % 2 == 0)
    .Select(n => n * n)
    .ToList(); // [4, 16, 36, 64, 100]

// Order
var sorted = numbers.OrderBy(n => n).ToList();
var sortedDesc = numbers.OrderByDescending(n => n).ToList();

// First/Last
var first = numbers.First();
var last = numbers.Last();
var firstEven = numbers.First(n => n % 2 == 0);
var maybeFirst = numbers.FirstOrDefault(n => n > 10);

// Aggregate
var sum = numbers.Sum();
var avg = numbers.Average();
var min = numbers.Min();
var max = numbers.Max();
var count = numbers.Count();

// Group
var users = new List { ... };
var byAge = users.GroupBy(u => u.Age);
foreach (var group in byAge)
{
    Console.WriteLine($"Age {group.Key}: {group.Count()} users");
}

// Distinct
var unique = numbers.Distinct().ToList();

// Skip/Take (paging)
var page2 = numbers.Skip(3).Take(3).ToList(); // [4, 5, 6]

// LINQ Tips
- Use ToList() to execute query
- LINQ is lazy (executed when iterated)
- Order matters for performance
- Use FirstOrDefault() for safety
- Use Any() instead of Count() > 0

💡 LINQ Tips

• Use ToList() to execute query
• LINQ is lazy (executed when iterated)
• Order matters for performance
• Use FirstOrDefault() for safety
• Use Any() instead of Count() > 0