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

        public Result Validate(FilterContext context)
        {
            Result result = new Result();

            // check for top level error.
            if (m_selectClauses == null || m_selectClauses.Count == 0)
            {
                result.Status = ServiceResult.Create(
                    StatusCodes.BadStructureMissing, 
                    "EventFilter does not specify any Select Clauses.");

                return result;
            }            

            if (m_whereClause == null)
            {
                result.Status = ServiceResult.Create(
                    StatusCodes.BadStructureMissing, 
                    "EventFilter does not specify any Where Clauses.");

                return result;
            }

            result.Status = ServiceResult.Good;

            // validate select clause.
            bool error = false;

            foreach (SimpleAttributeOperand clause in m_selectClauses)
            {
                ServiceResult clauseResult = null;

                // check for null.
                if (clause == null)
                {
                    clauseResult = ServiceResult.Create(
                        StatusCodes.BadStructureMissing, 
                        "EventFilterSelectClause cannot be null in EventFilter SelectClause.");

                    result.SelectClauseResults.Add(clauseResult);
                    error = true;
                    continue;
                }

                // validate clause.
                clauseResult = clause.Validate(context, 0);

                if (ServiceResult.IsBad(clauseResult))
                {
                    result.SelectClauseResults.Add(clauseResult);
                    error = true;
                    continue;
                }
                
                // clause ok.                    
                result.SelectClauseResults.Add(null);
            }

            if (error)
            {
                result.Status = StatusCodes.BadEventFilterInvalid;
            }
            else
            {
                result.SelectClauseResults.Clear();
            }
            
            // validate where clause.          
            result.WhereClauseResult = m_whereClause.Validate(context);

            if (ServiceResult.IsBad(result.WhereClauseResult.Status))
            {
                result.Status = StatusCodes.BadEventFilterInvalid;
            }

            return result;
        }
    }