using System;

​

public class Program

{

    public static void Main()

    {

        decimal answer = 0;

        string savedOperator = "-";

        decimal savedNumber = 8.8m;

        string txtBox = "5.0";

        if (savedOperator == "+")

        {

            answer = savedNumber + Convert.ToDecimal(txtBox);

            txtBox = answer.ToString();

            savedOperator = "";

        }

​

        if (savedOperator == "-")

        {

            answer = savedNumber - Convert.ToDecimal(txtBox);

            txtBox = answer.ToString();

            savedOperator = "";

        }

​

        if (savedOperator == "*")

        {

            answer = savedNumber * Convert.ToDecimal(txtBox);

            txtBox = answer.ToString();

            savedOperator = "";

        }

​

        if (savedOperator == "/")

        {

            answer = savedNumber / Convert.ToDecimal(txtBox);

            txtBox = answer.ToString();

            savedOperator = "";

        }

​

        Console.WriteLine(answer);

    }

}