MSBuild 3.5

I have the following project structure:

trunk/MainSolution.sln
trunk/Build/MyBuild.Proj
trunk/Library/...
trunk/etc...

So far, I've been using the following property to find out the project root folder:

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

Everything was working great, until I tried using a copy task that relied on this path. It is not resolving correctly. I basically end up getting something like this which is not valid:

C:\Projects\MyProject\Trunk\Build\..\CodeAnalysis\myfile.xml

So basically, I need to get the full path for (MSBuildProjectDirectory)'s Parent.

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