If you ever incorporate XmlSerialization into your applications, you're probably aware of the SGEN.exe utility.  If not, you should become familiar with it.  Without going into details about it, suffice it to say that by using sgen.exe you can greatly improve the performance of your applications that rely on serialization (e.g., Web Service clients, et al).  Without it, your applications suffer in part because the .NET Framework generates a dynamic assemblies at runtime for the Xml-Serializable types in your application when first serialized.  Note that this hit is taken 'up front' and doesn't affect the runtime performance as much as the initialization performance of your application.

Well, since VS 2005 MS has included an option within the GUI on the Build tab called “Generate serialization assembly” with three options: Auto, On, and Off.  Unfortunately, though the intentions were there, this option is largely unusable for several reasons.  The same problems have carried over to VS 2008 with no changes.  On the bright side, however, there are other options at our disposal.

1. Use the sgen.exe from the command line.  Fun an exciting indeed!
2. Set up a Post-build event command line referencing sgen.exe.  Even more exciting!
3. The best option is to use the <SGen> MSBuild task which automates the process for us.  Awesome!

In fact, the main reason to use the <SGen> MSBuild task is to turn off the /proxytypes switch that the GUI throws in for us when the “Generate serialization assembly” is set to “On” which only has any meaning for Web Services.  Edit your .csproj file, dropping the following XML:

<Target Name="GenSerializationAssembly"
        DependsOnTargets="AssignTargetPaths;Compile;ResolveKeySource"
        Inputs="$(MSBuildAllProjects);@(IntermediateAssembly)"
        Outputs="$(OutputPath)$(_SGenDllName)">
  <SGen BuildAssemblyName="$(TargetFileName)"
        BuildAssemblyPath="$(OutputPath)"
        References="@(ReferencePath)"
        ShouldGenerateSerializer="true"
        UseProxyTypes="false"
        KeyContainer="$(KeyContainerName)"
        KeyFile="$(KeyOriginatorFile)"
        DelaySign="$(DelaySign)"
        ToolPath="$(SGenToolPath)">
    <Output TaskParameter="SerializationAssembly" ItemName="SerializationAssembly" />
  </SGen>
</Target>
<Target Name="AfterBuild" DependsOnTargets="GenSerializationAssembly" />

Now, when you build your project you'll get another DLL  with the name “assemblyname.XmlSerializers.dll”.  Simply deploy this DLL with your application to take advantage of the pre-generated serialization library.

Note:  Thanks to Kiwidude for the pointer on the MSBuild task.