Opc.Ua.ElementOperand.Validate C# (CSharp) Method

        public override ServiceResult Validate(FilterContext context, int index)
        {
            if (m_index < 0)
            {
                return ServiceResult.Create(
                    StatusCodes.BadFilterOperandInvalid, 
                    "ElementOperand specifies an Index that is less than zero ({0}).", 
                    m_index);
            }

            if (m_index <= index)
            {
                return ServiceResult.Create(
                    StatusCodes.BadFilterOperandInvalid, 
                    "ElementOperand references an element that precedes it in the ContentFilter.", 
                    m_index);
            }

            if (m_index >= Parent.Parent.Elements.Count)
            {
                return ServiceResult.Create(
                    StatusCodes.BadFilterOperandInvalid, 
                    "ElementOperand references an element that does not exist.", 
                    m_index);
            }

            return ServiceResult.Good;
        }