I often need to refer to tools and libraries in my SVN repository that live in a folder not underneath the current project folder.  For instance I may need to use NUnit from trunk\store\web, but NUnit lives under trunk\tools\nunit\bin. 

Relative to the trunk, I know where to find NUnit, but where's the trunk?  The trunk may be checked out to c:\source\mytrunk or e:\work, or even the user's documents and settings folder.  This means I must use relative paths to NUnit from the current project directory, but this gets tricky if I have an external MSBuild target file that is shared between projects.

The only way to tell the shared imported targets file where things are relative to it, is to have the parent MSBuild script to pass in a property telling it where the root of the source control folder is (or where the tools directory is).  In my case this is the 'SourceDirectory' property which should point to the root of my source control folder hierarchy.  This gets annoying after a while since everywhere I include the shared targets file I first must create the SourceDirectory property first, like so:

<PropertyGroup>

  <SourceDirectory>$(MSBuildProjectDirectory)\..\..</SourceDirectory>

</PropertyGroup>

Yes this works pretty well, but it makes the shared imported targets file not-so-self contained and I have to repeat this over and over again in every project file that wants to include the shared targets files, which in my case is every single csproj file.  I have to do this since my project files live at varying depths in the folder hierarchy.  Instead of specifying this property everywhere, I've put this at the top of my shared targets file:

<PropertyGroup Condition="'$(SourceDirectory)' == ''">

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\Master.proj')">$(MSBuildProjectDirectory)</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\Master.proj')">$(MSBuildProjectDirectory)\..</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\..\Master.proj')">$(MSBuildProjectDirectory)\..\..</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\..\..\Master.proj')">$(MSBuildProjectDirectory)\..\..\..</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\..\..\..\Master.proj')">$(MSBuildProjectDirectory)\..\..\..\..</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\..\..\..\..\Master.proj')">$(MSBuildProjectDirectory)\..\..\..\..\..</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\..\..\..\..\..\Master.proj')">$(MSBuildProjectDirectory)\..\..\..\..\..\..</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\..\..\..\..\..\..\Master.proj')">$(MSBuildProjectDirectory)\..\..\..\..\..\..\..</SourceDirectory>

  <SourceDirectory Condition="'$(SourceDirectory)' == '' And Exists('$(MSBuildProjectDirectory)\..\..\..\..\..\..\..\..\Master.proj')">$(MSBuildProjectDirectory)\..\..\..\..\..\..\..\..</SourceDirectory>

</PropertyGroup>

What this does is look for a Master.proj file in each directory traversing upwards until it finds one, at which point the SourceDirectory property becomes set.  I can do this since I know that I only ever have one Master.proj file in the root of my SVN repository, and I never have a project more than 4 folders deep (although here I support 9 levels)  It's kind of cheesy, but it works well and saves me from having to do anything other than just import the shared targets file.

<Import Project="$(MSBuildProjectDirectory)\..\..\utils\gp.vs.targets" />

Hopefully Microsoft will add a well known property that allows you to get the current directory of the current build file, rather than just the parent script directory like MSBuildProjectDirectory does now.