using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        //Good input for int value

        Console.WriteLine(RarityRepository.GetStringValue(2));

        //Good input for string value

        Console.WriteLine(RarityRepository.GetIntValue("Rare"));

        //Bad input for int value

        Console.WriteLine(RarityRepository.GetStringValue(35));

        //Bad input for string value

        Console.WriteLine(RarityRepository.GetIntValue("Super Rare"));

    }

}

​

public static class RarityRepository

{

    private static Dictionary<int, string> _values = new Dictionary<int, string>()  

    {  

        { 1, "Very Common" },

        { 2, "Common" },

        { 3, "Standard" },

        { 4, "Rare" },

        { 5, "Very Rare" },

    };

    public static string GetStringValue(int input)

    { 

        string output = string.Empty;  // returns empty string if no matches are found

        _values.TryGetValue(input, out output);

        return output;

    }

​

    public static int GetIntValue(string input)

    {

        var result = _values.FirstOrDefault(x => string.Compare(x.Value, input, true) == 0);

        if (result.Equals(default(KeyValuePair<int,string>)))

        {

            return -1; // returns -1 if no matches are found

        }

        return result.Key;

    }

}