The name does not exist in the current context?

Question

I'm a total noob in c#, since today. I couldn't find a good tutorial or anything, that could solve this obviously dumb problem. Basically, I try to translate a program from Python to C#. Normally in Python I define constants in the constructor. Where the hell should I put them in c#? I tried to put them in the constructor then I put them in Main(), because there was this error. But the error persists.

static void Main(string[] args)
    {
    var _top = 0
    ...
    }
public string[] topToken()
    {
        if (_top < _tokens.Count())
        { return _tokens[_top];}

Answer 1

_top is declared inside Main, so it's not going to have visibility inside the topToken method. It's a local variable, scoped only to Main.

To give your variables visibility for the entire class, you need to declare them outside of any method.

Ex:

public class SomeClass
{
    public int someVariable; // all methods in SomeClass can see this

    public void DoIt() {
      // we can use someVariable here
    }
}

Note, by makeing someVariable public, it also means other we can access it directly. For example:

SomeClass x = new SomeClass();
x.someVariable = 42;

If you want to prevent this and only allow the methods/properties/etc. of the class to be able to see the someVariable variable, you can declare it as private.

In cases where you need a public variable, it's usually best to declare it like this (this is an example of an auto-implemented property):

public class SomeClass
{
    public int SomeVariable { get; set; }

    public void DoIt() {
      // we can use SomeVariable here
    }
}

This uses

Answer 2

if you want _top to be available outside of the Main method, place it here:

int _top = 0; //here instead
static void Main(string[] args)
{
    ...
}
public string[] topToken()
{
    if (_top < _tokens.Count())
    { return _tokens[_top];}
}

Answer 3

Change your code to this:

const int _top = 0;

static void Main(string[] args)
    {
    ...
    }
public string[] topToken()
    {
        if (_top < _tokens.Count())
        { return _tokens[_top];}

To make _top accessible throughout your class you have to declare it as a field or a constant. A field requires actual storage while a constant is simply replaced by the actual value by the compiler. As you described _top as a constant I decided to declare it as such.

If you need a field and not a constant you have to declare it static because it is accessed in a static method:

static int _top = 0;

Because there is no public or protected in the declaration of _top it is private to the class. If you prefer you can add private in front of the declaration but that will be the default if the visibility is missing.