syntax error - C# The name ' ... ' doesn't exist in the current context

Question

I'm new in C# and I try to learn it from the very basics, but I stuck with classes. I made my first example to practice which is working properly but when I add a little complexity I get an error:

"The name 'iArcher' doesn't exist in the current context."

Please help to explain what's wrong and suggest a proper (and easy) solution.

Thanks!

using System;

namespace Units
{
    class Archer
    {
        public int id;
        public int hp;
        public float speed;
        public float attack;
        public float defence;
        public float range;

        public void setProp(int id, int hp, float sp, float at, float de, float ra)
        {
            this.id = id;
            this.hp = hp;
            speed   = sp;
            attack  = at;
            defence = de;
            range   = ra;
        }

        public string getProp()
        {
            string str = "ID        = " + id +      "
" +
                         "Health    = " + hp +      "
" +
                         "Speed     = " + speed +   "
" +
                         "Attack    = " + attack +  "
" +
                         "Defence   = " + defence + "
" +
                         "Range     = " + range +   "
" ;

            return str;
        }

        static void Main(string[] args)
        {
            string input = Console.ReadLine();

            if (input == "create: archer")
            {
                Archer iArcher = new Archer();
                iArcher.setProp(100, 20, 4f, 8f, 3.5f, 25f);
            }

            if (input == "property: archer")
            {
                Console.WriteLine(iArcher.getProp());    // ERROR!
            }
            Console.ReadLine();
        }
    }
}

Answer 1

C# has scopes. An item within a scope can see everything in the scopes that contain it, but outer scopes can't see within inner scopes. You can read about scopes here.

Take your example:

if (input == "create: archer")
{
    Archer iArcher = new Archer();
    iArcher.setProp(100, 20, 4f, 8f, 3.5f, 25f);
}

iArcher is in the scope of your if statement, so code outside that if statement can't see it.

To resolve this, move the definition or iArcher outside the if statement:

Archer iArcher = new Archer();
if (input == "create: archer")
{
    iArcher.setProp(100, 20, 4f, 8f, 3.5f, 25f);
}

if (input == "property: archer")
{
    Console.WriteLine(iArcher.getProp());
}

---

Note that this now leaves you with another problem: input cannot be both "create: archer" and "property: archer".

One solution might be to move reading user input inside a loop, while keeping iArcher outside that loop:

Archer iArcher = new Archer();
string input = null;

while ((input = Console.ReadLine()) != "exit")
{
    if (input == "create: archer")
    {
        iArcher.setProp(100, 20, 4f, 8f, 3.5f, 25f);
    }
    else if (input == "property: archer")
    {
        Console.WriteLine(iArcher.getProp());
    }
}

To exit the loop simply type "exit" as the input.