Aggregation Operator

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Aggregation Operator

Several standard query operators are defined for aggregating a sequence of values into a single value. The most general aggregation operator is Aggregate, which is defined like this:

public static U Aggregate<T, U>(this IEnumerable<T> source,

U seed, Func<U, T, U> func) {

U result = seed;

foreach (T element in source)

result = func(result, element);

return result;

}

The Aggregate operator makes it simple to perform a calculation over a sequence of values. Aggregate works by calling the lambda expression once for each member of the underlying sequence. Each time Aggregate calls the lambda expression, it passes both the member from the sequence and an aggregated value (the initial value is the seed parameter to Aggregate). The result of the lambda expression replaces the previous aggregated value, and Aggregate returns the final result of the lambda expression.

For example, this program uses Aggregate to accumulate the total character count over an array of strings:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleApplication4

{

class Program

{

static void Main(string[] args)

{

string[] names = { "Albert", "Burke", "Connor", "David",

"Everett", "Frank", "George", "Harris"};

     int count = names.Aggregate(0, (c, s) => c + s.Length);

    Console.WriteLine(count);

     Console.ReadLine();

    }

}

OutPut: