How to set SGEN toolpath in Msbuild to target 3.5 framework

I've just upgraded a project from VS2008 to VS2010 but I'm still targeting the 3.5 framework.

In my project file I have a custom task to run SGEN to generate my XmlSerializers.dll. However the version of sgen being run targets the 4.0 framework. As a result, when I run my application I get the error message:

"Could not load file or assembly 'XXXX.XXXX.XmlSerializers' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded."

The Sgen task looks like this:

  <Target Name="AfterBuild" DependsOnTargets="AssignTargetPaths;Compile;ResolveKeySource" Inputs="$(MSBuildAllProjects);@(IntermediateAssembly)" Outputs="$(OutputPath)$(_SGenDllName)">
    <!-- Delete the file because I can't figure out how to force the SGen task. -->
    <Delete Files="$(TargetDir)$(TargetName).XmlSerializers.dll" ContinueOnError="true" />
    <SGen BuildAssemblyName="$(TargetFileName)" BuildAssemblyPath="$(OutputPath)" References="@(ReferencePath)" ShouldGenerateSerializer="true" UseProxyTypes="false" KeyContainer="$(KeyContainerName)" KeyFile="$(KeyOriginatorFile)" DelaySign="$(DelaySign)" ToolPath="$(SGenToolPath)">
      <Output TaskParameter="SerializationAssembly" ItemName="SerializationAssembly" />
    </SGen>
  </Target>

There's the ToolPath="$(SGenToolPath)". How do I make it run the version that targets 3.5?

There's a similar question here but it doesn't help me much.

I have solved this by manually configuring the ToolPath to point to the old (version 2.0.50727.3038) version of sgen.exe

On my machine, this is in: C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin

I changed the ToolPath attribute to be:

ToolPath="C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin"

and this solved the problem.

It seems, by default, it's running the new 4.0 framework version in: C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\NETFX 4.0 Tools

Hope this helps somebody else.