private string CreatePostfixNotation()
        {
            char[] operators = new char[] { '|', '+', '-', '*', '/', '(', ')' };
            operatorsStack.Push("|");

            InfixNotation = InfixNotation.Replace(" ", string.Empty);
            InfixNotation = InfixNotation + "|";
            int position = 0;

            while (position < InfixNotation.Length)
            {
                int length = InfixNotation.IndexOfAny(operators, position) - position;
                if (length == 0)
                {
                    length = 1;//in case next block is operator
                }
                string block = InfixNotation.Substring(position, length);
                position += length;

                AddBlockToStacks(block);
            }

            StringBuilder  result   = new StringBuilder();
            Stack <string> tmpStack = new Stack <string>(postfixNotationStack);

            foreach (var n in tmpStack)
            {
                result.Append(n);
                result.Append(" ");
            }

            return(result.ToString());
        }