Using .Net what limitations (if any) are there in using the XmlSerializer?

by

I generally find the XmlSerializer to be a poor choice for any POCO that’s more than just a DTO. If you require specific XML, you can go the Xml*Attribute and/or IXmlSerializable route – but you’re left with an object pretty mangled.

For some purposes, it still an obvious choice – even with it’s limitations. But, for simply storing and reloading data, I’ve found BinaryFormatter to be a much easier choice with less pitfalls.

Here’s a list of some annoyances with XmlSerializer – most I’ve been bitten by at one point or another, others I found over at MSDN:

  • Requires a public, no args constructor
  • Only serializes public read/write properties and fields
  • Requires all types to be known
  • Actually calls into get_* and set_*, so validation, etc. will be run. This may be good or bad (think about the order of the calls as well)
  • Will only serialize IEnumerable or ICollection collections conforming to specific rules

The XmlSerializer gives special treatment to classes that implement IEnumerable or ICollection. A class that implements IEnumerable must implement a public Add method that takes a single parameter. The Add method’s parameter must be of the same type as is returned from the Current property on the value returned from GetEnumerator, or one of that type’s bases.

A class that implements ICollection (such as CollectionBase) in addition to IEnumerable must have a public Item indexed property (indexer in C#) that takes an integer, and it must have a public Count property of type integer. The parameter to the Add method must be the same type as is returned from the Item property, or one of that type’s bases. For classes that implement ICollection, values to be serialized are retrieved from the indexed Item property, not by calling GetEnumerator.

  • Does not serialize IDictionary
  • Uses dynamically generated assemblies, which may not get unloaded from the app domain.

To increase performance, the XML serialization infrastructure dynamically generates assemblies to serialize and deserialize specified types. The infrastructure finds and reuses those assemblies. This behavior occurs only when using the following constructors:

XmlSerializer.XmlSerializer(Type)
XmlSerializer.XmlSerializer(Type, String)

If you use any of the other constructors, multiple versions of the same assembly are generated and never unloaded, which results in a memory leak and poor performance.

  • Cannot serialize ArrayList[] or List<T>[]
  • Has other weird edge cases

The XmlSerializer cannot be instantiated to serialize an enumeration if the following conditions are true: The enumeration is of type unsigned long (ulong in C#) and the enumeration contains any member with a value larger than 9,223,372,036,854,775,807.

The XmlSerializer class no longer serializes objects that are marked as [Obsolete].

You must have permission to write to the temporary directory (as defined by the TEMP environment variable) to deserialize an object.

  • Requires reading .InnerException to get any useful info on errors

More Related Contents:

  1. Deserializing empty xml attribute value into nullable int property using XmlSerializer
  2. “Type not expected”, using DataContractSerializer – but it’s just a simple class, no funny stuff?
  3. Can I serialize Anonymous Types as xml?
  4. Can Json.NET serialize / deserialize to / from a stream?
  5. Using Json.NET converters to deserialize properties
  6. What are the deficiencies of the built-in BinaryFormatter based .Net serialization?
  7. Serializing private member data
  8. What is the correct way to make a custom .NET Exception serializable?
  9. Can I use a Regex in an XPath expression?
  10. Best way to get InnerXml of an XElement?
  11. XML – Data At Root Level is Invalid
  12. Simplest way to have a configuration file in a Windows Forms C# application
  13. Serialize a nullable int
  14. How to localize when JSON-serializing?
  15. What is the correct format to use for Date/Time in an XML file
  16. How to deserialize a JObject to .NET object
  17. Does .NET 4 have a built-in JSON serializer/deserializer?
  18. Error Deserializing Xml to Object – xmlns=” was not expected
  19. DataContractSerializer vs XmlSerializer: Pros and Cons of each serializer
  20. How to use XPath with XElement or LINQ?
  21. Does .Net 4.5 support XML 1.1 yet (for characters invalid in XML 1.0)?
  22. replace WCF built-in JavascriptSerializer with Newtonsoft Json.Net json serializer
  23. Any way to make DataContractJsonSerializer serialize Dictionaries properly?
  24. How do I specify XML serialization attributes to support namespace prefixes during deserialization in .NET?
  25. WCF Disable Deserialization Order Sensitivity
  26. How do you use XMLSerialize for Enum typed properties in c#?
  27. JSON serialization of array with polymorphic objects
  28. Performance: XDocument versus XmlDocument
  29. What’s the best way to jSON serialize a .NET DataTable in WCF?
  30. Serializing a list of Key/Value pairs to XML

Leave a Comment