Opc.Ua.Server.BaseInstanceSource.ReadAttributeValue C# (CSharp) Method

        public DataValue ReadAttributeValue(
            IOperationContext    context, 
            ExpandedNodeId       typeDefinitionId,
            IList<QualifiedName> relativePath,
            uint                 attributeId,
            NumericRange         indexRange)
        {           
            lock (DataLock)
            {         
                // check for match on the event type being searched. 
                if (!Server.TypeTree.IsTypeOf(TypeDefinitionId, typeDefinitionId))
                {
                    return new DataValue(StatusCodes.BadNotSupported);
                }

                // find the target.
                NodeSource target = this;

                if (relativePath != null && relativePath.Count > 0)
                {                     
                    target = Find(relativePath, 0);

                    if (target == null)
                    {
                        return new DataValue(StatusCodes.BadNotSupported);
                    }
                }
                    
                // read the attribute value.
                DataValue dataValue = new DataValue();
                
                ServiceResult result = target.Read(context, attributeId, dataValue);

                if (ServiceResult.IsBad(result))
                {
                    return new DataValue(result.StatusCode);
                }

                // apply any index range.
                object value = dataValue.Value;

                result = indexRange.ApplyRange(ref value);

                if (ServiceResult.IsBad(result))
                {
                    return new DataValue(result.StatusCode);
                }

                dataValue.Value = value;

                // return the value.
                return dataValue;                
            }
        }