C# LINQ Aggregation Methods

Following examples show how to use LINQ aggregation methods defined in Enumerable class.

Enumerable.Sum

Returns sum of values in numeric collection.

numbers:	8 2 6 3

int result = numbers.Sum();

result:	19

Returns zero for empty collection.

numbers:	(empty)

int result = numbers.Sum();

result:	0

Enumerable.Max

Returns maximal value in numeric collection.

numbers:	8 2 6 3

int result = numbers.Max();

result:	8

Throws InvalidOperationException for empty collection.

numbers:	(empty)

int result = numbers.Max();

(exception)

Enumerable.Min

Returns minimal value in numeric collection.

numbers:	8 2 6 3

int result = numbers.Min();

result:	2

Throws InvalidOperationException for empty collection.

numbers:	(empty)

int result = numbers.Min();

(exception)

Enumerable.Count

Returns number of items in a collection.

items:	A B C D

int result = items.Count();

result:	4

Returns zero for empty collection.

items:	(empty)

int result = items.Count();

result:	0

Enumerable.LongCount

Returns number of items in a collection. The result is of type long (Int64), so the number of items can be greater than Int32.MaxValue (2,147,483,647).

items:	A B C D

long result = items.LongCount();

result:	4

Returns zero for empty collection.

items:	(empty)

long result = items.LongCount();

result:	0

Enumerable.Average

Returns average value of numeric collection.

numbers:	8 2 6 3

double result = numbers.Average();

result:	4.75

Throws InvalidOperationException for empty collection.

numbers:	(empty)

double result = numbers.Average();

(exception)

Enumerable.Aggregate

Aggregate method applies a function to each item of a collection. In this example the function to be applied is adding (operator +).

numbers:	8 2 6 3

int sum = numbers.Aggregate( func: (result,item) => result+item );

sum:	19

Throws InvalidOperationException for empty collection.

numbers:	(empty)

int sum = numbers.Aggregate( func: (result,item) => result+item );

(exception)

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