C# program for Getting First N Prime Number

In this article we will discuss with you the program for getting the first N prime number using console application in c#.net:

Step1: Take a new console application using c# as a language in the Visual studio.

Step2: Read an input from the User in this Variable “int_Number” for storing how many prime number you want to generate.

Step3: Now if that input number is 1 then the simply prime number will be 1 or if input number is 2 then the prime number will “1 and 2” otherwise we have to compute it through the below step

• We will test the values starting from 3 and loop till we get the “prime no count” is equal to the “input number”.
• Here I have assigned “int_PrimeNo_Count” to 2 since 1 and 2 is first two prime nos.
•  Now we have to loop from 2 till that number which we are testing for prime number and Start dividing that number from 2 till that number, If it’s divisible by any of the number before that i.e. “number-1” then it means that it’s not a prime number otherwise it is a prime number.
• If it is prime number then increment the “int_PrimeNo_Count” and add it to the list of prime no in the string variable “str_PrimeNO”.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace First_N_Prime

{

    Class Program

    {

        static void Main()

        {

            int int_Number;

            int i, int_PrimeNo_Count;

            string str_PrimeNO;

            str_PrimeNO = "1 2";

            Console.WriteLine("Please enter how many prime no you want to print?");

            int_Number = int.Parse(Console.ReadLine());

            if (int_Number == 1)

            {

                str_PrimeNO = "1";

            }

            else if (int_Number == 2)

            {

                str_PrimeNO = "1 2";

            }

            else

            {

                //Start dividing the value from 3 i.e. the value of j and increment j

                 // value till we get  int_PrimeNo_Count = int_Number    

                int j = 3;

                //we have 1 and 2 as prime no hence count is 2 and increment it when you  

                 // get the next prime no

                int_PrimeNo_Count = 2;

                //till you have n no of prime number

                while (int_PrimeNo_Count != int_Number)

                {

                    for (i = 2; i <= j; i++)

                    {

                        //Divide that number starting with 2 till that number

                        if (j % i == 0)

                        {

                            break;

                        }

                    }

                    //if it is the last number then means that it's a prime no,

                    //add it to the prime no list and increment the primeNo counter

                    if (j == i)

                    {

                        str_PrimeNO = str_PrimeNO + " " + i;

                        int_PrimeNo_Count++;

                    }

                    j++;

                }

            }

           

            Console.WriteLine(str_PrimeNO);

            Console.ReadLine();

        

  

        }

    }

}

Output:-