Develop Reference

Dynamic Link Library - include NuGet package libraries in final DLL in Visual Studio [duplicate]

I want to merge one .NET DLL assembly and one C# Class Library project referenced by a VB.NET Console Application project into one command-line console executable.
I can do this with ILMerge from the command-line, but I want to integrate this merging of reference assemblies and projects into the Visual Studio project. From my reading, I understand that I can do this through a MSBuild Task or a Target and just add it to a C#/VB.NET Project file, but I can find no specific example since MSBuild is large topic. Moreover, I find some references that add the ILMerge command to the Post-build event.
How do I integrate ILMerge into a Visual Studio (C#/VB.NET) project, which are just MSBuild projects, to merge all referenced assemblies (copy-local=true) into one assembly?
How does this tie into a possible ILMerge.Targets file?
Is it better to use the Post-build event?

The "MSBuild ILMerge task" (or MSBuild.ILMerge.Task) NuGet package makes this process quite simple. It defaults to merging any "copy local" references into your main assembly.
Note: Although the packages have similar names, this one is different from ILMerge.MSBuild.Tasks that Davide Icardi mentioned in his answer. The one I'm suggesting here was first published in August 2014.

Here an alternative solution:
1) Install ILMerge.MSBuild.Tasks package from nuget
PM> Install-Package ILMerge.MSBuild.Tasks
2) Edit the *.csproj file of the project that you want to merge by adding the code below:
<!-- Code to merge the assemblies into one:setup.exe -->
<UsingTask TaskName="ILMerge.MSBuild.Tasks.ILMerge" AssemblyFile="$(SolutionDir)\packages\ILMerge.MSBuild.Tasks.1.0.0.3\tools\ILMerge.MSBuild.Tasks.dll" />
<Target Name="AfterBuild">
<ItemGroup>
<MergeAsm Include="$(OutputPath)$(TargetFileName)" />
<MergeAsm Include="$(OutputPath)LIB1_To_MERGE.dll" />
<MergeAsm Include="$(OutputPath)LIB2_To_MERGE.dll" />
</ItemGroup>
<PropertyGroup>
<MergedAssembly>$(ProjectDir)$(OutDir)MERGED_ASSEMBLY_NAME.exe</MergedAssembly>
</PropertyGroup>
<Message Text="ILMerge #(MergeAsm) -> $(MergedAssembly)" Importance="high" />
<ILMerge InputAssemblies="#(MergeAsm)" OutputFile="$(MergedAssembly)" TargetKind="SameAsPrimaryAssembly" />
</Target>
3) Build your project as usual.

Some more information that might be useful to some people implementing Scott Hanselman's solution.
When I first set this up it would complain about not being able to resolve references to System.Core, etc.
It is something to do with .NET 4 support. Including a /lib argument pointing to the .NET 4 Framework directory fixes it (in fact just include the $(MSBuildBinPath)).
/lib:$(MSBuildBinPath)
I then found that IlMerge would hang while merging. It was using a bit of CPU and a lot of RAM but wasn't outputting anything. I found the fix on stackoverflow of course.
/targetplatform:v4
I also found that some of the MSBuild properties used in Scott's blog article relied on executing MsBuild from the project's directory, so I tweaked them a bit.
I then moved the targets & ilmerge.exe to the tools folder of our source tree which required another small tweak to the paths...
I finally ended up with the following Exec element to replace the one in Scott's original article:
<Exec Command=""$(MSBuildThisFileDirectory)Ilmerge.exe" /lib:$(MSBuildBinPath) /targetplatform:v4 /out:#(MainAssembly) "$(MSBuildProjectDirectory)\#(IntermediateAssembly)" #(IlmergeAssemblies->'"%(FullPath)"', ' ')" />
UPDATE
I also found Logic Labs answer about keeping the CopyLocal behaviour and just excluding ilMerged assemblies from CopyLocal essential if you are using Nuget packages. Otherwise you need to specify a /lib argument for each package directory of referenced assemblies that aren't being merged.

The article Mixing Languages in a Single Assembly in Visual Studio seamlessly with ILMerge and MSBuild at http://www.hanselman.com/blog/MixingLanguagesInASingleAssemblyInVisualStudioSeamlesslyWithILMergeAndMSBuild.aspx demonstrates how to use ILMerge and MSBuild within a Visual Studio Project.

One issue I found with the article at: http://www.hanselman.com/blog/MixingLanguagesInASingleAssemblyInVisualStudioSeamlesslyWithILMergeAndMSBuild.aspx.
If you have any references that you do not wish to ILMerge then the code in the article fails because it overrides the default CopyLocal behaviour to do nothing.
To fix this - Instead of:
<Target Name="_CopyFilesMarkedCopyLocal"/>
Add this entry to the targets file instead (.NET 3.5 only) (to filter out the non-ilmerge copylocal files, and treat them as normal)
<Target Name="AfterResolveReferences">
<Message Text="Filtering out ilmerge assemblies from ReferenceCopyLocalPaths" Importance="High" />
<ItemGroup>
<ReferenceCopyLocalPaths Remove="#(ReferenceCopyLocalPaths)" Condition="'%(ReferenceCopyLocalPaths.IlMerge)'=='true'" />
</ItemGroup>
</Target>

This is a great article that will show you how to merge your referenced assemblies into the output assembly. It shows exactly how to merge assemblies using msbuild.

My 2 cents - I picked up #Jason's response and made it work for my solution where I wanted to generate the *.exe in the bin/Debug folder with all *.dlls inside the same folder.
<Exec Command=""$(SolutionDir)packages\ILMerge.2.13.0307\Ilmerge.exe" /wildcards /out:"$(SolutionDir)..\$(TargetFileName)" "$(TargetPath)" $(OutDir)*.dll" />
Note: This solution is obviously hardcoded into the ILMerge nuget package version. Please let me know if you have some suggestions to improve.

Edit the *.csproj file of the project that you want to merge by adding the code below:
<Target Name="AfterBuild" Condition=" '$(ConfigurationName)' == 'Release' " BeforeTargets="PostBuildEvent">
<CreateItem Include="#(ReferenceCopyLocalPaths)" Condition="'%(Extension)'=='.dll'">
<Output ItemName="AssembliesToMerge" TaskParameter="Include" />
</CreateItem>
<Exec Command=""$(SolutionDir)packages\ILMerge.3.0.29\tools\net452\ILMerge.exe" /internalize:"$(MSBuildProjectPath)ilmerge.exclude" /ndebug /out:#(MainAssembly) "#(IntermediateAssembly)" #(AssembliesToMerge->'"%(FullPath)"', ' ')" />
<Delete Files="#(ReferenceCopyLocalPaths->'$(OutDir)%(DestinationSubDirectory)%(Filename)%(Extension)')" />
</Target>
Notes:
Replace $(SolutionDir)packages\ILMerge.3.0.29\tools\net452\ILMerge.exe with whatever path you have the ILMerge.exe in.
You can remove the Condition in the target to also merge on Debug but then the Debugger might not work
If you are not excluding anything you can remove: /internalize:"$(MSBuildProjectPath)ilmerge.exclude"

Check out this article by Jomo. He has a quick process to hack ILMerge into the msbuild system
http://blogs.msdn.com/jomo_fisher/archive/2006/03/05/544144.aspx

How to exclude one project out of multiple project from one solution during building using MSBuild in command prompt? [duplicate]

I need to build a solution, but exclude one project. How should I do it?
I searched a lot about this issue, but nothing could help.
An ItemGroup section rises the following exception:
Invalid element . Unknown task or datatype.
PropertyGroup also rises the exception.
Below is my code sample:
<project name="TI 8.1.6 build script">
<ItemGroup>
<Solution Include="${ROOT}\Core\TI Core.sln" Exclude="${ROOT}\Utilities\DTS Indexing Service\Tdi.Origami.IndexUpdaterServiceSetup\Tdi.Origami.IndexUpdaterServiceSetup.wixproj"/>
</ItemGroup>
...
</project>
How can I do this?

You can exclude projects at the solution level for a specific build configuration by using the Configuration Manager Dialog in Visual Studio:
Then you can simply invoke msbuild on the solution file specifying the build configuration to use:
msbuild /property:Configuration=Release MySolution.sln

The solution suggested by Enrico is the most versatile solution that would work always. An alternative solution might be to use a <MSBuild> task directly. This will work for you if you have all your project files under a particular directory, or be able to easily enumerate all projects you want to build (i.e. number of projects in your solution is not very big).
For example, this MSBuild file will build every project under your current directory except for a specific project:
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<ItemGroup>
<MyProjectReferences Include="**\*.*proj" />
<MyProjectReferences Exclude="Utilities\DTS Indexing Service\Tdi.Origami.IndexUpdaterServiceSetup\Tdi.Origami.IndexUpdaterServiceSetup.wixproj" />
</ItemGroup>
<Target Name="BuildAllExceptWixProject">
<MSBuild Projects="#(MyProjectReferences)" Targets="Build" />
</Target>
</Project>
Then you can build that using command line msbuild <myproject> /t:BuildAllExceptWixProject

In your solution file (.sln), remove the Build.0 entries. For example:
Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "MyProject", "MyProject.vcxproj", "{2281D9E7-5261-433D-BB04-176A61500CA3}"
EndProject
GlobalSection(ProjectConfigurationPlatforms) = postSolution
{2281D9E7-5261-433D-BB04-176A61500CA3}.Debug|x86.Build.0 = Debug|x64
If you delete this "Build.0" entry, it will load in the solution fine, but will not be built, either through the GUI or via external MSBuild.

Since VS 2019 and MSBuild 16.7, the right way is to use Solution filters. Ref

create a master.proj file:
in another ItemGroup add DefaultExclude properties for programs - put it in front of the solution
-- BA was Canadian
Configuration=Release
Release
drop the master.proj into the directory with the programs and msbuild the master.proj
compiles everything except... that HelloWorld

Change the referenced dll in a SSIS script task at build / deploy or runtime

Recently I have added all of our SSIS projects into a continuous integration pipeline. The projects are built using MSBuild in TeamCity, packaged and pushed to a nuget feed. We deploy them using Octopus and some hand cranked PowerShell built on the back os SQL server management objects (SMO). It all works, with the exception of one project. The project in question contains some script tasks which reference an external assembly. That assembly is built in the same pipeline and its assembly version numbers are updated by part of the process. The problem lies in the fact that the SSIS project now references a strong named dll in the GAC which does not exist because the version numbers have changed.
Does anyone know of a way to either updated the reference at build time on the CI server or override the version number at the point of deployment?

I know this post is quite old but it has been viewed a lot so here's a solution I have found.
You need to include a 'targets' file for the build.
Here's an example Targets file:
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<E10BOs>C:\Integrations\E10 Uplifts\Epicor 10.2.600.3</E10BOs>
</PropertyGroup>
<Target Name="BeforeResolveReferences">
<CreateProperty Value="$(E10BOs);$(AssemblySearchPaths)">
<Output TaskParameter="Value" PropertyName="AssemblySearchPaths" />
</CreateProperty>
</Target>
</Project>
The property group E10BOS (and there can be more than 1) then defines the path to the dll's of the version you want to build against.
It needs to be saved as myTargetsFile.targets
Then in a regular VS project you could add this line to the project file (outside of VS in notepad)
<Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
<Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), myTargetsFile.targets))\myTargetsFile.targets" />
</Project>
This uses GetDirectoryNameOfFileAbove to search up the folder tree until it finds you targets file and then imports it. Very useful if you have a lot of different projects all requiring a version change and you don't have to figure out any relative paths!
In SSIS however this doesn't seem to work.
What does is hard-wiring the path to the targets file in the package .dtsx file, again edit it in notepad and add the following line (you will probably see the csharp entry near the end of the project tag as before:
<Import Project="C:\Integrations\E10 Uplifts\Epicor 10.2.600.3\myTargetsFile.targets" />
This will pass through the information of the project references into the scripts.
Then with all of you projects using a targets file changing the version is done by changing the path to the version folder you want them to use.
Hope that helps?

Web.config transformation causing an error when building [duplicate]

I can run my Asp.Net MVC 2 application without an issue on my local computer. Just Run / Debug.
But if I have already built it, I can't publish it! I have to clean the solution and publish it again. I know this is not system critical, but it's really annoying. "One Click Publish" is not "Clean solution and then One click publish"
The exact error is as follows:
Error 11 It is an error to use a
section registered as
allowDefinition='MachineToApplication'
beyond application level. This error
can be caused by a virtual directory
not being configured as an application
in IIS.
I suspect it's something to do with the Web.Config in the Views folder, but then why only after I build once previously. And just to note, the app works fine once published.

i had the same problem with my MVC apps. it was frustrating because i still wanted my views to be checked, so i didn't want to turn off MvcBuildViews
luckily i came across a post which gave me the answer. keep the MvcBuildViews as true, then you can add the following line underneath in your project file:
<BaseIntermediateOutputPath>[SomeKnownLocationIHaveAccessTo]</BaseIntermediateOutputPath>
And make that folder not in your project's folder. Works for me. It's not a perfect solution, but it's good for the moment. Make sure you remove the package folder (located inside the obj\Debug and/or obj\Release folder) from your project folder otherwise you'll keep getting the error.
FWIW, MS know about this error...

I deleted everything out of my obj/Debug folder and it fixed this error. This allowed me to leave in the
<MvcBuildViews>true</MvcBuildViews>
option in my project file (which comes in handy with the T4MVC T4 template).
Edit:
This can be achieved much easier by simply using the "Build" -> "Rebuild Solution" menu (because what rebuild actually does is clear the obj/Debug folder and then build solution).

I'm using this workaround on the MS Connect page for this error. It cleans all obj and temp files under your project (all configurations) before running AspNetCompiler.
Modify the MvcBuildViews target in
your project file so that it depends
on the targets that clean up the
packaging files that Visual Studio has
created. These targets are included in
web application projects
automatically.
All packaging files will be deleted
every time that the MvcBuildViews
target executes.
<Target Name="MvcBuildViews" AfterTargets="AfterBuild" Condition="'$(MvcBuildViews)'=='true'" DependsOnTargets="CleanWebsitesPackage;CleanWebsitesPackageTempDir;CleanWebsitesTransformParametersFiles;">
<AspNetCompiler VirtualPath="temp" PhysicalPath="$(MSBuildProjectDirectory)" />
</Target>

This problem occurs when there is web project output (templated web.config or temporary publish files) in the obj folder. The ASP.NET compiler used isn't smart enough to ignore stuff in the obj folder, so it throws errors instead.
Another fix is to nuke the publish output right before calling <AspNetCompiler>. Open your .csproj and change this:
<Target Name="MvcBuildViews" AfterTargets="AfterBuild" Condition="'$(MvcBuildViews)'=='true'">
<AspNetCompiler VirtualPath="temp" PhysicalPath="$(WebProjectOutputDir)" />
</Target>
to this:
<Target Name="MvcBuildViews" AfterTargets="AfterBuild" Condition="'$(MvcBuildViews)'=='true'">
<ItemGroup>
<ExtraWebConfigs Include="$(BaseIntermediateOutputPath)\**\web.config" />
<ExtraPackageTmp Include="$([System.IO.Directory]::GetDirectories("$(BaseIntermediateOutputPath)", "PackageTmp", System.IO.SearchOption.AllDirectories))" />
</ItemGroup>
<Delete Files="#(ExtraWebConfigs)" />
<RemoveDir Directories="#(ExtraPackageTmp)" />
<AspNetCompiler VirtualPath="temp" PhysicalPath="$(WebProjectOutputDir)" />
</Target>
That will delete all web.configs under \obj, as well as all PackageTmp folders under \obj.

If you are using Web Publish, you can set MvcBuildViews=false and PrecompileBeforePublish=true, which precompiles after the copy to the temporary folder (immediately before publish/package).
NOTE: PrecompileBeforePublish is only supported by the "new" Web Publishing Pipeline stack (VS2010 SP1 + Azure SDK or VS2012 RTM). If you're using VS2010 RTM, you'll need use one of the alternative methods.

Regarding the solution by jrummell, the setting:
DependsOnTargets="CleanWebsitesPackage;CleanWebsitesPackageTempDir;CleanWebsitesTransformParametersFiles;"
It works in VS 2010, but not in VS 2012. In 2012 you have to put:
DependsOnTargets="CleanWebsitesPackage;CleanWebsitesWPPAllFilesInSingleFolder;CleanWebPublishPipelineIntermediateOutput"
Source:
VS 2010:
C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v10.0\Web\Microsoft.Web.Publishing.targets
VS 2012:
C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v11.0\Web\Microsoft.Web.Publishing.targets

I know this has been answered but I just wanted to add something interesting I found.
I had set the "MvcBuildViews" to false in the project, deleted all bin and obj folders and I was still getting the error. I found that there was a ".csproj.user" file that still had "MvcBuildViews" set to true.
I deleted the ".csproj.user" file and then it all worked.
So make sure if you are changing your csproj file that you either change or delete the ".csproj.user" file also.

I had this problem as well, so I created a Pre-Build Event in the project properties to Clean the output directories(${projectPath}\bin,${projectPath}\obj\${ConfigurationName}). On another project I was also getting this error, even with the cleaning event in place. On the second project I was compiling the views as listed in the project file:
<MvcBuildViews>true</MvcBuildViews>
I changed the true to false, and it no longer complained about that error, but still ran correctly. I won't claim I know exactly what was causing the second error, but at least it got me moving forward for the time being.

The problem has to do with the intermediate files, but there is another solution which consist in cleaning up those intermediate files before builnding the views.
This solution has been included in some version of VS, but I can only say that I had the problem in VS 2013 Update 5. (See the "Beware" below, it could be fixed in this version, but not working only in my particular non-standard case).
I borrowed the soltuion from Error: allowDefinition='MachineToApplication' beyond application level on Visual Studio Connect.
The solution consist in including these lines to the web application project (.csproj file) which handle the deletion of the offedning intermediate files:
<!--Deal with http://connect.microsoft.com/VisualStudio/feedback/details/779737/error-allowdefinition-machinetoapplication-beyond-application-level,
we will need to clean up our temp folder before MVC project starts the pre-compile-->
<PropertyGroup>
<_EnableCleanOnBuildForMvcViews Condition=" '$(_EnableCleanOnBuildForMvcViews)'=='' ">true</_EnableCleanOnBuildForMvcViews>
</PropertyGroup>
<Target Name="CleanupForBuildMvcViews" Condition=" '$(_EnableCleanOnBuildForMvcViews)'=='true' and '$(MVCBuildViews)'=='true' " BeforeTargets="MvcBuildViews">
<ItemGroup>
<_PublishTempFolderNamesToCleanup Include="Database;TransformWebConfig;CSAutoParameterize;InsertAdditionalCS;ProfileTransformWebConfig;Package;AspnetCompileMerge" />
</ItemGroup>
<!--Force msbuild to expand all the wildcard characters so to get real file paths-->
<CreateItem Include="#(_PublishTempFolderNamesToCleanup->'$(BaseIntermediateOutputPath)**\%(identity)\**\*')">
<Output TaskParameter="Include" ItemName="_EvaluatedPublishTempFolderNamesToCleanup" />
</CreateItem>
<Delete Files="#(_EvaluatedPublishTempFolderNamesToCleanup)" />
</Target>
Beware: for some reason, probably because I included it myself in the project, my build target for building the views was named "BuildViews", instead of "MvcBuildViews", so I had to modify the BeforeTargets attribute accordingly. I also simplified the target, by removing the PropertyGroup and simplifying the condition, like this:
<Target Name="CleanupForBuildMvcViews" Condition="'$(MVCBuildViews)'=='true' " BeforeTargets="BuildViews">
<ItemGroup>
<_PublishTempFolderNamesToCleanup Include="Database;TransformWebConfig;CSAutoParameterize;InsertAdditionalCS;ProfileTransformWebConfig;Package;AspnetCompileMerge" />
</ItemGroup>
<!--Force msbuild to expand all the wildcard characters so to get real file paths-->
<CreateItem Include="#(_PublishTempFolderNamesToCleanup->'$(BaseIntermediateOutputPath)**\%(identity)\**\*')">
<Output TaskParameter="Include" ItemName="_EvaluatedPublishTempFolderNamesToCleanup" />
</CreateItem>
<Delete Files="#(_EvaluatedPublishTempFolderNamesToCleanup)" />
</Target>

In my case i saw that when i have MvcBuildViews and PrecompileDuringPublish as both true - was what was causing this issue.
So i removed the PrecompileDuringPublish and that solution worked for me and i have not faced this problem since.

Out-of-place builds with C#

I just finished setting up an out-of-place build system for our existing C++ code using inherited property sheets, a feature that seems to be specific to the Visual C++ product. Building out-of-place requires that many of the project settings be changed, and the inherited property sheets allowed me to change all the necessary settings just by attaching a property sheet to the project. I am migrating our team from C++/MFC for UI to C# and WPF, but I need to provide the same out-of-place build functionality, hopefully with the same convenience. I cannot seem to find a way to do this with C# projects - I first looked to see if I could reference an MsBuild targets file, but could not find a way to do this. I know I could just use MsBuild for the whole thing, but that seems more complicated than necessary. Is there a way I can define a macro for a directory and use it in the output path, for example?

I'm not quite sure what an "out-of-place" build system is, but if you just need the ability to copy the compiled files (or other resources) to other directories you can do so by tying into the MSBuild build targets.
In our projects we move the compiled dlls into lib folders and put the files into the proper locations after a build is complete. To do this we've created a custom build .target file that creates the Target's, Property's, and ItemGroup's that we then use to populate our external output folder.
Our custom targets file looks a bit like this:
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<ProjectName>TheProject</ProjectName>
<ProjectDepthPath>..\..\</ProjectDepthPath>
<ProjectsLibFolder>..\..\lib\</ProjectsLibFolder>
<LibFolder>$(ProjectsLibFolder)$(ProjectName)\$(Configuration)\</LibFolder>
</PropertyGroup>
<Target Name="DeleteLibFiles">
<Delete Files="#(LibFiles-> '$(ProjectDepthPath)$(LibFolder)%(filename)%(extension)')" TreatErrorsAsWarnings="true" />
</Target>
<Target Name="CopyLibFiles">
<Copy SourceFiles="#(LibFiles)" DestinationFolder="$(ProjectDepthPath)$(LibFolder)" SkipUnchangedFiles="True" />
</Target>
<ItemGroup>
<LibFiles Include=" ">
<Visible>false</Visible>
</LibFiles>
</ItemGroup>
</Project>
The .csproj file in Visual Studio then integrates with this custom target file:
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="3.5" ... >
...
<Import Project="..\..\..\..\build\OurBuildTargets.targets" />
<ItemGroup>
<LibFiles Include="$(OutputPath)$(AssemblyName).dll">
<Visible>false</Visible>
</LibFiles>
</ItemGroup>
<Target Name="BeforeClean" DependsOnTargets="DeleteLibFiles" />
<Target Name="AfterBuild" DependsOnTargets="CopyLibFiles" />
</Project>
In a nutshell, this build script first tells MSBuild to load our custom build script, then adds the compiled file to the LibFiles ItemGroup, and lastly ties our custom build targets, DeleteLibFiles and CopyLibFiles, into the build process. We set this up for each project in our solution so only the files that are updated get deleted/copied and each project is responsible for it's own files (dlls, images, etc).
I hope this helps. I apologize if I misunderstood what you mean by out-of-place build system and this is completely useless to you!

Is there a way I can define a macro for a directory and use it in the output path
Have you looked at the pre-build and post-build events of a project?

Actually, pre-build and post-build events seem to be solely a place to add batch-file type commands. This would not help me to set up standard build directories for our projects, unfortunately. And having these events create batch files seems like a very 1980's approach for a modern language like C#, IMO.
After digging some more, and experimenting, I have found that you can add an <Import> directive into your .csproj file. When you do this, the IDE pops up a warning dialog that there is an unsafe entry point in your project - but you can ignore this, and you can make it not appear at all by editing a registry entry, evidently. So this would give me a way to get the variables containing the directory paths I need into the .csproj file.
Now to get the Output Path to refer to it - unfortunately when you add a string like "$(MySpecialPath)/Debug" to the Output Path field, and save the project, the $ and () chars are converted to hex, and your file get's put in a Debug directory under a directory named "$(MySpecialPath)". Arrgghh. If you edit the .csproj file in a text editor, you can set this correctly however, and it seems to work as long as the <Import> tag appears before the <PropertyGroup> containing the Output Path.
So I think the solution for me will be to create a standard OurTeam.targets MsBuild file in a standard location, add an installer for changing the registry so it doesn't flag warnings, and then create custom project templates that <Import> this file, and also set the Output Path to use the properties defined in the OurTeam.targets file. Sadly, this is more work and a less elegant solution than the property sheet inheritance mechanism in C++.