Sum of First N Natural Numbers in C#

Sum of first n natural numbers in C# – Learn how to calculate Sum of First N natural Numbers using Mathematical formula and adding from 1 to N in sequential order. also Learn how  to program in C#  using Mathematical formula and adding  in sequential order.

Natural Numbers are the Positive integers like 1,2,3……
1 is the starting Natural Number.

we have 2 methods to find sum of N natural Numbers

Method -1
To find the sum of first 5 natural numbers, we have solution like this 1+2+3+4+5 =15.
To find sum of N natural numbers , we have solution like this 1+2+….+N

Method -2
To compute This in Mathematical formula

SUM of N natural Numbers = N(N+1)/2

for Example to find first 5 natural numbers we can follow above for calculation.

SUM of 5 natural Numbers = 5(5+1)/2
                              =  5*6/2;
                              = 15

Sum of first n natural numbers in C#

below are the examples to calculate in Method -1 and in Method-2 process

Example1-C# program to find sum of N natural Numbers with Method-1 using for loop

using System;
 class Program
    {
        static void Main(string[] args)
        {
            int i, num=20, sum = 0;
            for (i = 1; i <= num; i++)
            {
                sum = sum + i;
               
            }
            Console.WriteLine("Sum of first" + num + 
            " natural numbers = " + sum);
        }
    }

Output
Sum of first20 natural numbers = 210

Example2-C# program to find sum of N natural Numbers with Method-1 using while loop

 class Program
    {
        static void Main(string[] args)
        {
            int i, num=20, sum = 0;

            i = 1;
            while( i <= num)
            {
                sum = sum + i;
                i++;
            }
            
            Console.WriteLine("Sum of first" + num +
            " natural numbers = " + sum);
        }
    }

Output
Sum of first20 natural numbers = 210

Example3-C# program to find sum of N natural Numbers with Method-2 using function

 class Program
    {
        static void Main(string[] args)
        {
            int  num=20, sum = 0;

            Program P = new Program();

            sum = P.findSum(num);
            
            Console.WriteLine("Sum of first" + num + 
             " natural numbers = " + sum);
        }
        int findSum(int n)
        {

            return ((n + 1) * n) / 2;
        }
    }

Output
Sum of first20 natural numbers = 210

Example4-program to find sum of N natural Numbers with Method-1 using recursive function

  class Program
    {
        static void Main(string[] args)
        {
            int  num=20, sum = 0;

            Program P = new Program();

            sum = P.findSum(num);
            
            Console.WriteLine("Sum of first" + num + 
             " natural numbers = " + sum);
        }
        int findSum(int n)
        {

            if (n != 0)
                return n + findSum(n - 1);
            else
                return n;
        }
    }

Output
Sum of first20 natural numbers = 210