Lesson 6: Aggregation & Element Operators in LINQ

Aggregation and element operators help you summarize and inspect sequences. They can compute totals, check conditions, or select a single item from a collection.

Aggregation Examples

Use these methods to compute results over a sequence:

• Count() — number of items.
• Sum() — numeric total.
• Average() — mean value.
• Min() / Max() — smallest or largest value.

var scores = new[] { 88, 92, 75, 100 };

Console.WriteLine(scores.Count());    // 4
Console.WriteLine(scores.Sum());      // 355
Console.WriteLine(scores.Average());  // 88.75
Console.WriteLine(scores.Min());      // 75
Console.WriteLine(scores.Max());      // 100

Quantifiers: Any & All

Any checks if any item matches a condition; All validates that every item matches.

var values = new[] { 5, 10, 15 };

Console.WriteLine(values.Any(v => v > 12)); // true
Console.WriteLine(values.All(v => v > 0));  // true

Single Item Operators

These operators return a single element or a safe default:

• First() / FirstOrDefault()
• Single() / SingleOrDefault()
• Last() / LastOrDefault()

var names = new[] { "Ava", "Leo", "Mia" };

Console.WriteLine(names.First());               // Ava
Console.WriteLine(names.FirstOrDefault());      // Ava
Console.WriteLine(names.Single(name => name == "Mia"));

Aggregation with Projection

You can aggregate projected values too.

var items = new[] { new { Price = 25m }, new { Price = 40m } };
var total = items.Sum(item => item.Price);

Lesson Summary