MSBuild and $(ProgramFiles) issue with 32/64 bits - visual-studio-2010

Question

I wrote a custom MSBuild task which calls SubWCRev.exe, an executable which (typically) resides in C:\Program Files\TortoiseSVN\bin, whether it's 32 or 64 bits, since TortoiseSVN provides both versions.
The problem is, Visual Studio 2010 only has a 32 bit version. So when my colleagues with a 64 bit box try to build using my shiny new task, $(ProgramFiles) resolves to C:\Program Files(x86) and it explodes saying that SubWCRev.exe cannot be found. Because they have the 64 bit version of TortoiseSVN, which lives in C:\Program Files!
Is there a better solution than hardcoding C:\Program Files in my msbuild script, or having everyone use the 32 bit version of TortoiseSVN? (Actually it's a C# project, I tinkered with the MSBuild code a bit)

Answer 1

Take a look it this:
<Project ToolsVersion="4.0" DefaultTargets="PrintValues" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<Target Name="PrintValues">
<PropertyGroup>
<MyProgramFiles>$(ProgramW6432)</MyProgramFiles>
<MyProgramFiles Condition="$(MyProgramFiles) == ''">$(ProgramFiles)</MyProgramFiles>
</PropertyGroup>
<Message Text="MyProgramFiles: $(MyProgramFiles)"/>
</Target>
</Project>
This lets MyProgramFiles resolve to "C:\Program Files" for both 32 and 64 bit Windows (The ProgramW6432 environment variable is empty on non-64 bit versions of Windows).

Answer 2

Use MSBuildExtensionsPath property instead of hardcoding the path.
Per MSDN:
The MSBuild subfolder under the \Program Files\ or \Program Files
(x86) folder. This path always points to the Program Files of the same
bitness as the window you are currently running in. For example, for a
32-bit window on a 64-bit machine, the path is to the Program Files
(x86) folder. For a 64-bit window on a 64-bit machine, the path is to
the Program Files folder. See also MSBuildExtensionsPath32 and
MSBuildExtensionsPath64.
Edit: To get to the 64 bit SVN folder, use :
<PropertyGroup>
<TortoiseSVNPath>$(MSBuildExtensionsPath64)\..\TortoiseSVN\bin</TortoiseSVNPath>
</PropertyGroup>
Another way is to check for existence of folders:
<PropertyGroup>
<TortoiseSVNPath Condition="Exists('$(PROGRAMFILES) (x86)')">$(PROGRAMFILES) (x86)\TortoiseSVN\bin</TortoiseSVNPath>
<TortoiseSVNPath Condition="$(TortoiseSVNPath) == ''">$(PROGRAMFILES)\TortoiseSVN\bin</TortoiseSVNPath>
</PropertyGroup>