How to fix this ISeries interface implementation in Class1?

Question

I am developing a series of numbers starting from Setstart(2) function from ISeries interface. I tried to implement this interface in Class1 but it threw an error to me. And I am getting stuck at this error and not been able to figure out to fix this. What am I missing? Please help

I tried to make all functions in the interface public I tried to remove public access specifier from interface

public interface ISeries {
    void Setstart (int a);
    int GetNext ();
    void Reset ();
}

class Class1 : ISeries {

    int val;
    void Setstart (int a) {
        val = a;
    }

    int GetNext () {
        return val++;
    }

    void Reset () {
        val = 0;
    }

    static void Main () {
        Class1 c = new Class1 ();
        c.Setstart (2);
        Console.WriteLine (c.GetNext ());
        c.Reset ();
        Console.WriteLine ();
    }
}

I expect the output to be 3 and 0 error is being generated

Answer 1

You need to make your methods public to be accessible outside from class which is missing other than that your code looks fine.

You need to make all the 3 methods public as per your scenario like :

public void Setstart (int a) {

and you will need to first add 1 and then return to get 3 as output as val++ will return the current value and then increment it by 1:

public int GetNext () {

        // return val++; // Post increment will not work according to question.
        val = val + 1;
        return val;
    }

Your class with complete implementation of Interface would be like following:

public class Class1 : ISeries {

    int val;
    public void Setstart (int a) {
        val = a;
    }

    public int GetNext () {
        val = val + 1;
        return val;
    }

    public void Reset () {
        val = 0;
    }
}

Answer 2

Your should try something like this.

Because you have to play with one variable so you have to make use of ref `keyword in this case.

and also you have to mark all the method inside a class as a public otherwise you were not be able to access those method inside main

Code:

using System;

namespace StackoverflowProblem
{
    public interface ISeries
    {
        void Setstart(ref int value);
        int GetNext(ref int value);
        void Reset(ref int value);
    }

    public class Class1 : ISeries
    {
        public int val { get; set; }

        public void Setstart(ref int value)
        {
            this.val = value;
        }

        public int GetNext(ref int value)
        {
            value = value + 1;
            this.val = value;

            return this.val;
        }

        public void Reset(ref int value)
        {
            // Resetting val.
            value = 0;
            this.val = value;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Class1 c = new Class1();

            int value = 2;
            c.Setstart(ref value);

            Console.WriteLine(" " + c.GetNext(ref value));

            c.Reset(ref value);
            Console.WriteLine();
        }
    }
}

Output:

Answer 3

val++ will incriment after returning the current value, ++val will increment first then return the value, you should now get 3, also make it proper scoped to access the methods from outside

class Class1 : ISeries {

int val;
public void Setstart (int a) {
    val = a;
}

public int GetNext () {
    return ++val;
}

public void Reset () {
    val = 0;
}

static void Main () {

    Class1 c = new Class1();
    c.Setstart(2);
    Console.WriteLine (c.GetNext());
    c.Reset();
    Console.WriteLine ("");
}

}