How to create natural language calculator

Question

i'm trying to create a simple natural language calculate. this is what i am trying to achieve, If i input the string "five plus six" the output should be answer: 11.

below i tried to create a Enum of numbers but for operators it does not accept strings,i use this so i can fetch and compare to the array input and covert respectively,could you please suggest what i can maybe use to store operators as words so? or suggest an article maybe.

code:

 public class EnumSample
  {
    enum Numbers: int
    {
      zero = 0,
      obne = 1,
      two = 2,
      three =3,
      four =4,
      five =5,
      six =6,
      seven=7,
      eight = 8,
      nine=9,
    };
    enum Operator
    {
      Add = "+",
      plus ="+",
      minus ="-",
      subtract ="-"
    };

    public static void Main()
    {
      int[] arr = new int[200];
      Console.Write("Get input");
      for (int i = 0; i < 200; i++)
      {
        Console.Write("element - {0} : ", i);
        arr[i] = Convert.ToInt32(Console.ReadLine());
      }

      foreach (int item in Enum.GetValues(typeof (Numbers)))
      {
        String name = Enum.GetName(typeof(Numbers), item);
        Console.WriteLine(name+item);
   
      }
      Console.Read();
    }
  }

Answer 1

I prefer use Dictionary instead Enum. Here is solution only for 2 value but you can figure out something by looking at this solution;

public class EnumSample
  {
    private static int Solve(string operation, int first, int second)
    {
      switch (operation)
      {
        case "plus":
        {
          return second + first;
        }
        case "add":
        {
          return second + first;
        }
        default:
          return second-first;
      }
    }
    public static void Main()
    {
      var numbersDic = new Dictionary<string, int>()
      {
        {"zero", 0},
        {"one", 1},
        {"two", 2},
        {"three", 3},
        {"four", 4},
        {"five", 5},
        {"six", 6},
        {"seven", 7},
        {"eight", 8},
        {"nine", 9}
      };
      Console.WriteLine("Get input");
      string[] word = Console.ReadLine()?.Split(' '); // spliting words {"five","plus","six"}
      
      if (word != null) 
        Console.Write(Solve(word[1], numbersDic[word[0]], numbersDic[word[2]]));
      //                plus , 5 , 6
      Console.Read();
    }
  }