What is MyAssembly.XmlSerializers.dll generated for?

Question

In .NET implementation, the XmlSerializer generates a temporary assembly for serializing/deserializing your classes (for performance reasons). It can either be generated on the fly (but it takes time on every execution), or it can be pregenerated during compilation and saved in this assembly you are asking about.

You can change this behaviour in project options (tab Compile -> Advanced Compile Options -> Generate serialization assemblies, Auto or On, respectively). The corresponding element in the project file is GenerateSerializationAssemblies, for example, <GenerateSerializationAssemblies>Auto</GenerateSerializationAssemblies>.

FYI. The exact steps to stop the XmlSerializers.dll from being auto-generated are:

1. In VS, right-click your project file and select "Properties"
2. Click the "Build" tab
3. Change the "Generate serialization assembly" dropdown from "Auto" to "Off"
4. Rebuild and it will be gone

I think this is the JIT (Just in time) compilation of XML serialisers for performance reasons.

You get the same thing with RegEx instances using the RegexOptions.Compiled option turned on.

I'm no .NET CLR expert, sorry for lack of precise technical detail.

*.XmlSerializers.dll are generated using the Sgen.exe [XML Serializer Generator Tool]

See Sgen.exe on MSDN

Typically the Sgen.exe is used in Post Build events of Projects. See if your project has a post build event which generates the *.XmlSerializers.dll