using System;

// see: https://stackoverflow.com/questions/13071823/convert-expression-from-a-textbox-to-math-expression-in-code-behind/13071974#13071974

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Eval("15 / 3"));

    }

    public static string Eval(string expr)

    {

        var temp = new System.Data.DataTable();

        return $"{temp.Compute(expr, string.Empty)}";

    }

}