using System;

using org.matheval;

public class Program

{

    public static void Main()

    {

        Expression taxExpr = new Expression("IF(LOWER(TAX_CODE)='vat',amount*10/100,IF(LOWER(TAX_CODE)='gst',amount*15/100,0))");

        taxExpr.Bind("TAX_CODE","GST");

        taxExpr.Bind("amount", 5005m);

        Decimal value = taxExpr.Eval<Decimal>();

        Console.WriteLine(value);

    }

}