public void Visit(UnaryExpression expression)
 {
     throw new NotImplementedException();
 }
        /// <summary>
        /// Visits a unary expression
        /// </summary>
        /// <param name="expression">The expression</param>
        /// <exception cref="ArgumentNullException">Thrown when the input parameter is null</exception>        
        public void Visit(UnaryExpression expression)
        {
            if (expression == null)
            {
                throw new ArgumentNullException("expression");
            }

            expression.Expression.Accept(this);
            if (result is int)
            {
                int param = (int)result;
                switch (expression.Type)
                {
                    case UnaryExpressionType.Not:
                        result = param != 0 ? 0 : 1;
                        break;
                    case UnaryExpressionType.BitNot:
                        result = ~param;
                        break;
                    case UnaryExpressionType.Positive:
                        result = +param;
                        break;
                    case UnaryExpressionType.Negative:
                        result = -param;
                        break;
                    case UnaryExpressionType.Dereference:
                        int value;
                        int pointerValue;
                        if (param == 1 || param == 0)
                        {
                            ValueExtractor ve = new ValueExtractor();
                            expression.Expression.Accept(ve);
                            string expr = ve.Expression;
                            if (context.TryResolveDereference(expr, out value, out pointerValue))
                            {
                                result = value;
                            }
                        }
                        else
                        {
                            IntPtr p = new IntPtr(param);
                            // only supports 32bit pointer here. To support 64bit, too much work to do
                            result = System.Runtime.InteropServices.Marshal.ReadInt32(p);
                        }
                        break;
                    default:
                        break;
                }
            }
            else if (result is string)
            {
                result = GetUnaryOperatorString(expression.Type) + result.ToString();
            }
        }