linq Standard Query Operators Aggregation Operations

Example

Aggregation operations computes a single value from a collection of values.

Aggregate

Performs a custom aggregation operation on the values of a collection.

Method Syntax

// Aggregate

var numbers = new int[] { 1, 2, 3, 4, 5 };

var product = numbers.Aggregate(1, (acc, n) => acc * n);

// product = 120

Query Syntax

// Not applicable.

---

Average

Calculates the average value of a collection of values.

Method Syntax

// Average

var numbers = new int[] { 1, 2, 3, 4, 5 };

var average = numbers.Average();

// average = 3

Query Syntax

// Not applicable.

---

Count

Counts the elements in a collection, optionally only those elements that satisfy a predicate function.

Method Syntax

// Count

var numbers = new int[] { 1, 2, 3, 4, 5 };

int count = numbers.Count(n => n % 2 == 0);

// count = 2

Query Syntax

// Not applicable.

---

LongCount

Counts the elements in a large collection, optionally only those elements that satisfy a predicate function.

Method Syntax

// LongCount

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

long count = numbers.LongCount();

// count = 10

Query Syntax

// Not applicable.

---

Max

Determines the maximum value in a collection. Throws exception if collection is empty.

Method Syntax

// Max

var numbers = new int[] { 1, 2, 3, 4, 5 };

var max = numbers.Max();

// max = 5

Query Syntax

// Not applicable.

---

Min

Determines the minimum value in a collection. Throws exception if collection is empty.

Method Syntax

// Min

var numbers = new int[] { 1, 2, 3, 4, 5 };

var min = numbers.Min();

// min = 1

Query Syntax

// Not applicable.

---

Min-/MaxOrDefault

Unlike other LinQ extensions Min() and Max() do not have an overload without exceptions. Therefor the IEnumerable must be checked for Any() before calling Min() or Max()

// Max

var numbers = new int[] { };

var max = numbers.Any() ? numbers.Max() : 0;

// max = 0

---

Sum

Calculates the sum of the values in a collection.

Method Syntax

// Sum

var numbers = new int[] { 1, 2, 3, 4, 5 };

var sum = numbers.Sum();

// sum = 15

Query Syntax

// Not applicable.