An aggregate operation computes a single value from a collection.

Methods

Aggregate

Aggregate<T1>(this IEnumerable<T> source, Func<T, T, T> function)

• Performs an operation on the first two elements in the collection.
• It takes that result and performs an operation on the next element…
• …and so on for all elements.

var nums = new[]{1,2,3,4};
var sum = nums.Aggregate( (a,b) => a + b);
Console.WriteLine(sum); // output: 10 (1+2+3+4)

Aggregate<T1>(this IEnumerable<T1> source, T2 seed, Func<T2, T1, T2> function)

• Same as a above, but uses a seed value to start:

var multipliers = new []{10,20,30,40};
var multiplied = multipliers.Aggregate(5, (a,b) => a * b);
Console.WriteLine(multiplied); //Output 1200000 ((((5*10)*20)*30)*40)

Average

Calculates the average value of a collection.

Count

Count<T1>(this IEnumerable<T1> source)
Counts the elements of a collection.

Count<T1>(this IEnumerable<T1> source, Func<T, Boolean> function)
Counts only those elements that satisfy a predicate function.

LongCount

Like count, but returns Int64 instead of Int32.

Max(By)

Returns the maximum value in a collection.

Min(By)

Returns the minimum value in a collection.

Sum

Calculates the sum of the values in a collection.