VS 2010 RTM - MSBuild Project file for App.config XML transformations.

AppConfig.Transformation.targets

<?xml version="1.0" encoding="utf-8" ?>
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <!-- 20110617 : Luke Smith : Imports Microsoft.WebApplication.targets for SP1 support. Added exists condition for when the TransformedConfig doesn't exist -->
  <!-- 20110224 : Ryan Milligan : Created OverrideAppConfigWithTargetPath target to fix ClickOnce deploy bug -->
  <!-- 20100827 : João Angelo   : Fixed bug when using Publish command within Visual Studio -->
  <PropertyGroup>
    <!-- Prevent circular dependency on Build target -->
    <PipelineDependsOnBuild>false</PipelineDependsOnBuild>
    <!-- Override project config file name (By default is set to Web.config) -->
    <ProjectConfigFileName>App.config</ProjectConfigFileName>
  </PropertyGroup>

  <!-- The transformation target (TransformWebConfig) in this targets file-->
  <Import Project="$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.targets" />

  <!-- Removes the need to set config files Build Action as Content -->
  <ItemGroup>
    <FilesForPackagingFromProject Include="$(ProjectConfigFileName)">
      <DestinationRelativePath>$(ProjectConfigFileName)</DestinationRelativePath>
    </FilesForPackagingFromProject>
  </ItemGroup>

  <!-- Insert transformation targets in the build process -->
  <PropertyGroup>
    <BuildDependsOn>
      TransformWebConfig;
      OverrideAppConfigWithTargetPath;
      $(BuildDependsOn);
      CopyTransformedConfig
    </BuildDependsOn>
  </PropertyGroup>
  
  <PropertyGroup>
    <TransformedConfig>$(TransformWebConfigIntermediateLocation)\transformed\App.config</TransformedConfig>
  </PropertyGroup>

  <!-- Overrides AppConfigWithTargetPath allowing the transformed config to be used for manifest generation -->
  <Target Name="OverrideAppConfigWithTargetPath">
    <ItemGroup>
      <AppConfigWithTargetPath Remove="@(AppConfigWithTargetPath)" />
      <AppConfigWithTargetPath Include="$(TransformedConfig)" Condition="'$(TransformedConfig)'!='' AND Exists('$(TransformedConfig)')">
        <TargetPath>$(TargetFileName).config</TargetPath>
      </AppConfigWithTargetPath>
    </ItemGroup>
  </Target>

  <!-- Copy transformed file to output directory -->
  <Target Name="CopyTransformedConfig" Condition="'$(TargetName)' != ''">
    <Copy Condition="Exists('$(TransformedConfig)')"
          SourceFiles="$(TransformedConfig)"          
          DestinationFiles="$(OutputPath)$(TargetName)$(TargetExt).config" />
    <Copy Condition="Exists('$(TransformedConfig)') And '$(TargetExt)' == '.exe'"          
          SourceFiles="$(TransformedConfig)"          
          DestinationFiles="$(OutputPath)$(TargetName).vshost.exe.config" />
  </Target>

  <!--        
  Override After Publish to support ClickOnce
  
  AfterPublish target replaces the untransformed config file copied to the
  deployment directory with the transformed one  
  -->
  <Target Name="AfterPublish">  
    <PropertyGroup>
      <DeployedConfig>$(_DeploymentApplicationDir)$(TargetName)$(TargetExt).config$(_DeploymentFileMappingExtension)</DeployedConfig>
    </PropertyGroup>
    <!-- Publish copies the unstransformed App.config to deployment directory so overwrite it -->
    <Copy Condition="Exists('$(DeployedConfig)')"
          SourceFiles="$(TransformedConfig)"
          DestinationFiles="$(DeployedConfig)" />
    </Target>
</Project>

I've add this to my project file as such

<Import Project="..\AppConfig.Transformation.targets" />

just before the UsingTask TaskName="TransformXml" and I'm getting an error on build:

Error   1   "obj\x86\Release\TransformWebConfig\transformed\App.config;obj\x86\Release\OsgExporter.Shell.exe.config" is an invalid value for the "ConfigFile" parameter of the "GenerateApplicationManifest" task. Multiple items cannot be passed into a parameter of type "Microsoft.Build.Framework.ITaskItem".  OsgExporter.Shell