A lot of run-time compilation is involved when the XmlSerializer is used. For better performance it is recommended to run sgen.exe to generate a serialization assembly to speed up the XML serialization. In a way, the idea behind SGen is the same as for NGen.
There is a Generate Serialization Assembly drop-down in the project settings in Visual Studio, but this covers only available Web service proxies. To have Visual Studio run SGen automatically for other types, you need to manually add the following lines to your project file:
<Target Name="AfterBuild" 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" />