Opc.Ua.ContentFilter.GetValue C# (CSharp) Method

        private object GetValue(FilterContext context, FilterOperand operand, IFilterTarget target)
        {
            // return the contained value for literal operands.
            LiteralOperand literal = operand as LiteralOperand;

            if (literal != null)
            {
                return literal.Value.Value;
            }

            // must query the filter target for simple attribute operands.
            SimpleAttributeOperand simpleAttribute = operand as SimpleAttributeOperand;

            if (simpleAttribute != null)
            {
                return target.GetAttributeValue(
                    context,
                    simpleAttribute.TypeDefinitionId,
                    simpleAttribute.BrowsePath,
                    simpleAttribute.AttributeId,
                    simpleAttribute.ParsedIndexRange);
            }

            // must query the filter target for attribute operands.
            AttributeOperand attribute = operand as AttributeOperand;

            if (attribute != null)
            {
                // AttributeOperands only supported in advanced filter targets.
                IAdvancedFilterTarget advancedTarget = target as IAdvancedFilterTarget;

                if (advancedTarget == null)
                {
                    return false;
                }

                return advancedTarget.GetRelatedAttributeValue(
                    context,
                    attribute.NodeId,
                    attribute.BrowsePath,
                    attribute.AttributeId,
                    attribute.ParsedIndexRange);
            }
            
            // recursively evaluate element operands.
            ElementOperand element = operand as ElementOperand;

            if (element != null)
            {
                return Evaluate(context, target, (int)element.Index);
            }
                    
            // oops - Validate() was not called.
            throw new ServiceResultException(StatusCodes.BadUnexpectedError, "FilterOperand is not supported.");
        }