Aggregation Function in LINQ

In LINQ, aggregation functions are those functions which are used to calculate a single value from the collection of the values. Real life example of aggregation function is calculating the annual rainfall occurred in 2018 according to readings collected whole year. Another example, the sum function is used to find the sum of the values present in the given array or sequence.

Following is the list of the methods that are used to perform aggregation operations:

Method	Description
Aggregate	It performs, a custom aggregation operation on the values of a collection.
Average	It calculates the average value of a collection of values.
Count	It counts the elements in a collection, optionally only those elements that satisfy a predicate function.
LongCount	It counts the elements in a large collection, optionally only those elements that satisfy a predicate function.
Max	It determines the maximum value in a collection.
Min	It determines the minimum value in a collection.
Sum	It calculates the sum of the values in a collection.

Example 1:

// C# program to illustrate how to
// find the sum of the given sequence
using System;
using System.Linq;

public class GFG {

    // Main Method
    static public void Main()
    {

        int[] sequence = {20, 40, 50, 68, 90,
                          89, 99, 9, 57, 69};

        Console.WriteLine("The sum of the given sequence is: ");

        // Finding sum of the given sequence
        // Using Sum function
        int result = sequence.Sum();
        Console.WriteLine(result);
    }
}

Output:

The sum of the given sequence is: 
591

Example 2:

// C# program to illustrate how to
// find the minimum and maximum value
// from the given sequence
using System;
using System.Linq;

public class GFG {

    // Main Method
    static public void Main()
    {

        int[] sequence = {201, 39, 50, 9, 7, 99};

        // Display the Sequence
        Console.WriteLine("Sequence is: ");

        foreach(int s in sequence)
        {
            Console.WriteLine(s);
        }

        // Finding the minimum value
        // from the given sequence
        // Using Min function
        int result1 = sequence.Min();

        Console.WriteLine("Minimum Value is: {0}", result1);

        // Finding the maximum value
        // from the given sequence
        // Using Max function
        int result2 = sequence.Max();

        Console.WriteLine("Maximum Value is: {0}", result2);
    }
}

Output:

Sequence is: 
201
39
50
9
7
99
Minimum Value is: 7
Maximum Value is: 201

Reference:

• https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/aggregation-operations