Linq to Xml VS XmlSerializer VS DataContractSerial

问题:

In my web method, I get an object of some third party C# entity class. The entity class is nothing but the DataContract. This entity class is quite complex and has properties of various types, some properties are collections too. Of course, those linked types are also DataContracts.

I want to serialize that DataContract entity into XML as part of business logic of my web service. I cannot use DataContractSerializer directly (on the object I receive in the web method) simply because the XML schema is altogether different. So the XML generated by DataContractSerializer will not get validated against the schema.

I am not able to conclude the approach I should follow for implementation. I could think of following implementation approaches:

1. LINQ to XML - This looks ok but I need to create XML tree (i.e. elements or XML representation of the class instance) manually for each type of object. Since there are many entity classes and they are linked to each other, I think this is too much of work to write XML elements manually. Besides, i'll have to keep modifying the XML Tree as and when the entity class introduces some new property. Not only this, the code where I generate XML tree would look little clumsy (at least in appearance) and would be harder to maintain/change by some other developer in future; he/she will have to look at it so closely to understand how that XML is generated.

2. XmlSerializer - I can write my own entity classes that represent the XML structure I want. Now, I need to copy details from incoming object to the object of my own classes. So this is additional work (for .NET too when code executes!). Then I can use XmlSerializer on my object to generate XML. In this case, I'll have to create entity classes and whenever third party entity gets modified, I'll have to just add new property in my class. (with XmlElement or XmlAttibute attributes). But people recommend DataContractSerializer over this one and so I don't want to finalize this unless all aspects are clear to me.

3. DataContractSerializer - Again here, I'll have to write my own entity class since I have no control over the third party DataContracts. And I need to copy details from incoming object to the object of my own classes. So this is additional work. However, since DataContractSerializer does not support Xml attributes, I'll have to implement IXmlSerializable and generate required Xml in WriteXml method. DataContractSerializer is faster than XmlSerializer, but again I'll have to handle the changes (in WriteXml) if third party entity changes.

Questions:

• Which approach is best in this scenario considering performance too?
• Can you suggest some better approach?
• Is DataContractSerializer worth considering (because it has better performance over XmlSerilaizer) when incoming entity class is subject to change?
• Should LINQ be really used for serialization? Or is it really good for things other than querying?
• Can XmlSerializer be preferred over LINQ in such cases? If yes, why?

回答1:

I agree with @Werner Strydom's answer.

I decided to use the XmlSerializer because code becomes maintainable and it offers performance I expect. Most important is that it gives me full control over the XML structure.

This is how I solved my problem:

I created entity classes (representing various types of Xml elements) as per my requirement and passed an instance of the root class (class representing root element) through XmlSerializer.

Small use of LINQ in case of 1:M relationship:

Wherever I wanted same element (say Employee) many times under specific node (say Department) , I declared the property of type List<T>. e.g. public List<Employee> Employees in the Department class. In such cases XmlSerializer obviously added an element called Employees (which is grouping of all Employee elements) under the Department node. In such cases, I used LINQ (after XmlSerializer serialized the .NET object) to manipulate the XElement (i.e. XML) generated by XmlSerializer. Using LINQ, I simply put all Employee nodes directly under Department node and removed the Employees node.

However, I got the expected performance by combination of xmlSerializer and LINQ.

Downside is that, all classes I created had to be public when they could very well be internal!

Why not DataContractSerializer and LINQ-to-XML?

• DataContractSerializer does not allow to use Xml attributes (unless I implement IXmlSerializable). See the types supported by DataContractSerializer.
• LINQ-to-XML (and IXmlSerializable too) makes code clumsy while creating complex XML structure and that code would definitely make other developers scratch their heads while maintaining/changing it.

Is there any other way?

• Yes. As mentioned by @Werner Strydom, you can very well generate classes using XSD.exe or tool like Xsd2Code and work directly with them if you are happy with the resulting classes.

回答2:

I'll pick XmlSerializer because its the most maintainable for a custom schema (assuming you have the XSD). When you are done developing the system, test its performance in its entirety and determine whether XML serialization is causing problems. If it is, you can then replace it with something that requires more work and test it again to see if there is any gains. But if XML serialization isn't an issue, then you have maintainable code.

The time it takes to parse a small snippet of XML data may be negligible compared to communicating with the database or external systems. On systems with large memory (16GB+) you may find the GC being a bottleneck in .NET 4 and earlier (.NET 4.5 tries to solve this), especially when you work with very large data sets and streams.

Use AutoMapper to map objects created by XSD.EXE to your entities. This will allow the database design to change without impacting the web service.

One thing that is great about LINQ to XML is XSD validation. However, that impacts performance.

回答3:

Another option is to utilize LINQ and Reflection to create a generic class to serialize your object to XML. A good example of this can be found at http://primecoder.blogspot.com/2010/09/how-to-serialize-objects-to-xml-using.html . I am not sure what your XML needs to look like at the end of the day, but if it is pretty basic this could do the trick. You would not need to make changes as your entity classes add/remove/change properties, and you could use this across all of your objects (and other projects if stored in a utility DLL).