Question

How do I make this program continue running after the user selects an option? Here is the code I have so far.

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

namespace calculator_extended
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Press A for addition");
            Console.WriteLine("Press S for subtraction");
            Console.WriteLine("Press M for Multiplication");
            Console.WriteLine("Press D for Divide");

            char c = Convert.ToChar(Console.ReadLine());

            int a = Convert.ToInt32(Console.ReadLine());
            int b = Convert.ToInt32(Console.ReadLine());

            switch (c)
            {
                case 'A':
                case 'a':
                    {
                        int d = add(a, b);
                        Console.WriteLine(d);
                        break;


                    }


                case 'S':
                case 's':
                    {
                        int d = sub(a, b);
                        Console.WriteLine(d);
                        break;
                    }

                case 'M':
                case 'm':
                    {
                        int d = mul(a, b);
                        Console.WriteLine(d);
                        break;
                    }

                case 'E':
                case 'e':
                    {
                        int d = div(a, b);
                        Console.WriteLine(d);
                        break;
                    }
                default:
                    {

                        Console.WriteLine("Please Enter the correct Character");
                        break;
                    }


            }
        }
            private static int add(int a, int b)
    {

                   return a + b;
    }
               private static int sub(int a, int b)
    {

                   return a - b;
    }
               private static int mul(int a, int b)
    {
                   return a * b;
    }
               private static int div(int a, int b)
    {

                   return a / b;
    }

        }
    }

Answer 1

Wrap your code with

while(true) {
    // Your code here

    // Don't forget to add a switch case for an Exit operation
    case 'q':
        Application.Exit();
}

If you’re new to programming, you should look into Loops – See Listing 4-2 – it’s a good example of what you’re trying to accomplish.

EDIT:
I realize you’re new to programming and I do think you should accomplish this by your own.
As it’s a basic problem, here’s a full solution

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

namespace calculator_extended
{
    class Program
    {
        static void Main(string[] args)
        {
            int d = 0;

            while (true)
            {
                Console.WriteLine("Press A for addition");
                Console.WriteLine("Press S for subtraction");
                Console.WriteLine("Press M for Multiplication");
                Console.WriteLine("Press D for Divide");

                char c = Convert.ToChar(Console.ReadLine());

                int a = Convert.ToInt32(Console.ReadLine());
                int b = Convert.ToInt32(Console.ReadLine());

                switch (c)
                {
                    case 'A':
                    case 'a':
                        d = add(a, b);
                        Console.WriteLine(d);
                        break;
                    case 'S':
                    case 's':
                        d = sub(a, b);
                        Console.WriteLine(d);
                        break;
                    case 'M':
                    case 'm':
                        d = mul(a, b);
                        Console.WriteLine(d);
                        break;
                    case 'E':
                    case 'e':
                        d = div(a, b);
                        Console.WriteLine(d);
                        break;
                    case 'q':
                    case 'Q':
                        Application.Exit();
                    default:
                        Console.WriteLine("Please Enter the correct Character");
                        break;
                }
            }
        }
        private static int add(int a, int b)
        {

            return a + b;
        }
        private static int sub(int a, int b)
        {

            return a - b;
        }
        private static int mul(int a, int b)
        {
            return a * b;
        }
        private static int div(int a, int b)
        {

            return a / b;
        }

    }
}