How fast is XmlSerializer?

Note: this entry has moved.

Have you ever wondered how does the XmlSerializer really works? Well, it creates a temporary assembly that is built by reflecting the type you pass to the constructor. Wait! Don't panic because of the "reflecting" word!
It does so only once per type, and it builds an extremely efficient pair of Reader/Writer classes that will handle serialization/ deserialization during the life of the AppDomain.

These classes inherit the public XmlSerializationReader and XmlSerializationWriter classes in the System.Xml.Serialization namespace. If you want to take a look at the generated code, add the following setting to the application configuration file (web.config for a web application):

<system.diagnostics>
  <switches>
    <add name="XmlSerialization.Compilation" value="4"/>
  </switches>
</system.diagnostics>

Now the serializer won't delete the temporary files generated in the process. For a web application, the files will be located in C:\Documents and Settings\[YourMachineName]\ASPNET\Local Settings\Temp, otherwise, they will be located in your current user Local Settings\Temp folder.
You will see code that is exactly what you would have to do if you wanted to efficiently load Xml in .NET: use nested while/if as you read, use XmlReader methods to move down the stream, etc. All the ugly code is there to make it really fast.

Special thanks to Chris Sells for his XmlSerializerCompiler utility.