C# Program to find the sum of a sequence

A sequence in C# is a collection of elements that can be processed using LINQ methods. To find the sum of a sequence, you can use several approaches including the Sum() method from LINQ, which provides a simple and efficient way to calculate the total.

The most common approach is using the LINQ Sum() method, which can be applied to any IEnumerable<T> collection.

Syntax

Following is the syntax for using the Sum() method −

// For numeric collections
collection.Sum();

// With selector function
collection.Sum(x => x.Property);

Using LINQ Sum() Method

The Sum() method calculates the sum of all numeric elements in a sequence −

using System;
using System.Linq;
using System.Collections.Generic;

public class Demo {
    public static void Main() {
        List<int> myList = new List<int> { 1, 2, 3, 4, 5 };
        
        Console.WriteLine("Elements in the sequence:");
        foreach (int element in myList) {
            Console.WriteLine(element);
        }
        
        int sum = myList.Sum();
        Console.WriteLine("Sum = {0}", sum);
    }
}

The output of the above code is −

Elements in the sequence:
1
2
3
4
5
Sum = 15

Using Sum() with Arrays

The Sum() method also works with arrays and other numeric sequences −

using System;
using System.Linq;

public class ArraySumDemo {
    public static void Main() {
        int[] numbers = { 10, 20, 30, 40, 50 };
        double[] decimals = { 1.5, 2.5, 3.5, 4.5 };
        
        int intSum = numbers.Sum();
        double doubleSum = decimals.Sum();
        
        Console.WriteLine("Integer array sum: " + intSum);
        Console.WriteLine("Double array sum: " + doubleSum);
    }
}

The output of the above code is −

Integer array sum: 150
Double array sum: 12

Using Traditional Loop Approach

You can also calculate the sum using a traditional for loop approach −

using System;
using System.Collections.Generic;

public class LoopSumDemo {
    public static void Main() {
        List<int> numbers = new List<int> { 5, 10, 15, 20, 25 };
        int sum = 0;
        
        foreach (int number in numbers) {
            sum += number;
        }
        
        Console.WriteLine("Numbers: " + string.Join(", ", numbers));
        Console.WriteLine("Sum using loop: " + sum);
    }
}

The output of the above code is −

Numbers: 5, 10, 15, 20, 25
Sum using loop: 75

Comparison of Approaches

Conclusion

The LINQ Sum() method provides the most efficient and readable way to calculate the sum of a numeric sequence in C#. For simple scenarios, it's preferred over traditional loops due to its conciseness and functional programming approach.