C# Online Compiler | .NET Fiddle

using System;
using System.Collections.Generic;

/*
	Fibonacci numbers and sequences
	https://en.wikipedia.org/wiki/Fibonacci_number
*/
public class Fibonacci
{	
	// this method computes the n-th Fibonacci number
	// e.g. for n = 8, the Fibonacci number is 21
	public int getFibonacciNumber(int n) {  
		if (n == 0 || n == 1) {
			return n;
		}
		else {
        	return getFibonacciNumber(n - 1) + getFibonacciNumber(n - 2);
		}
	}
	
	// this method computes the n-th Fibonacci sequence
	// e.g. for n = 8, the Fibonacci sequence is [1, 1, 2, 3, 5, 8, 13, 21]
	public List<int> getFibonacciSequence(int n) {
		List<int> f_series = new List<int>();
		
		/*
			>>> add your code here:
			>>> - use the method 'public int getFibonacciNumber(int n)' to compute Fibonacci numbers
			>>> - use 'this' to invoke the 'getFibonacciNumber' method. 'this' refers to the current 'Fibonacci' instance. An example is shown on the next line.
		*/
		this.getFibonacciNumber(n);		
		
		return f_series;
	}
	
	// Main method (application entry point)
	public static void Main()
	{
		int n = 8;
		// a new 'Fibonacci' instance is created. This is necessary because 'getFibonacciNumber' and 'getFibonacciSequence' are non-static methods.
		Fibonacci f = new Fibonacci();
		Console.WriteLine("Fibonacci number for n = " + n + ": " + f.getFibonacciNumber(n));
		
		/* 
			>>> add your code here:
			>>> - use the method 'public List<int> getFibonacciSeries(int n)' to compute the Fibonacci sequence
			>>> - format the sequence and print it to the console as follows:
			>>>   "Fibonacci sequence for n = 8: [1, 1, 2, 3, 5, 8, 13, 21]"
		*/
	}
}

 
using System;
using System.Collections.Generic;
​
/*
    Fibonacci numbers and sequences
    https://en.wikipedia.org/wiki/Fibonacci_number
*/
public class Fibonacci
{   
    // this method computes the n-th Fibonacci number
    // e.g. for n = 8, the Fibonacci number is 21
    public int getFibonacciNumber(int n) {  
        if (n == 0 || n == 1) {
            return n;
        }
        else {
            return getFibonacciNumber(n - 1) + getFibonacciNumber(n - 2);
        }
    }
    
    // this method computes the n-th Fibonacci sequence
    // e.g. for n = 8, the Fibonacci sequence is [1, 1, 2, 3, 5, 8, 13, 21]
    public List<int> getFibonacciSequence(int n) {
        List<int> f_series = new List<int>();