How to call methods with constructor, in C#?

Question

Here is an assignment from a class that I was never able to complete.

I make a constructor and try to call the method. It never works. I really don't know what I am doing wrong here. I ask for an input and readline, then type my constructor, but it won't call. How am I supposed to call this?

public static int RomToNum(String rom)
{
    StringBuilder temp = new StringBuilder();
    int ret = 0;
    char[] letters = rom.ToArray();
    foreach (char item in letters)
    {
        if (item == 'M')
            ret += 1000;
        if (item == 'D')
            ret += 500;
        if (item == 'C')
            ret += 100;
        if (item == 'L')
            ret += 50;
        if (item == 'X')
            ret += 10;
    }

    for (int x = 0; x < letters.Length; x++)
    {
        if (letters[x] == 'I' && !letters.Contains('V'))
        {
            ret += 1;
        }
        else
        {
            if (letters[x] == 'I' && x != letters.Length-1)
            {
                ret += 4;
                break;
            }
            else if (letters[x] == 'I' && x == letters.Length-1)
            {
                ret += 6;
                break;
            }
        }
    }
    return ret;

}

Answer 1

I honestly don't know why you want to call the method with a constructor rather than what Precious1tj posted. But If you want to use the constructor to call the method you can do this:

class Program
    {
        static void Main(string[] args)
        {
            Class2 c2 = new Class2("X"); //outputs '10' once it's instantiated

            Console.ReadKey();
        }
    }

    class Class2
    {
        //overloaded ctor
        public Class2(string rom)
        {
            Console.WriteLine(RomToNum(rom));
        }
        public static int RomToNum(String rom)
        {
            StringBuilder temp = new StringBuilder();
            int ret = 0;
            char[] letters = rom.ToArray();
            foreach (char item in letters)
            {
                if (item == 'M')
                    ret += 1000;
                if (item == 'D')
                    ret += 500;
                if (item == 'C')
                    ret += 100;
                if (item == 'L')
                    ret += 50;
                if (item == 'X')
                    ret += 10;
            }

            for (int x = 0; x < letters.Length; x++)
            {
                if (letters[x] == 'I' && !letters.Contains('V'))
                {
                    ret += 1;
                }
                else
                {
                    if (letters[x] == 'I' && x != letters.Length - 1)
                    {
                        ret += 4;
                        break;
                    }
                    else if (letters[x] == 'I' && x == letters.Length - 1)
                    {
                        ret += 6;
                        break;
                    }
                }
            }
            return ret;

        }
    }

The downside of calling the method from the constructor is that you'll have to create a new object of the class whenever you want to evaluate a new Roman Numeral.

Answer 2

Since you're calling it in another class

you use

    CurrentClass.RomToNum("String Values");

You dont need to create an object for the class in order to reference this method because it is a static method