I have tried several solutions for this problem. Enough to know I do not know enough about MSBuild to do this elegantly but I feel like there should be a method.

I have a set of libraries for working with .net projects. A few of the projects utilize System.Web.Mvc - which recently released Version 2 - and we are looking forward to the upgrade. Currently sites which reference this library reference it directly by the project(csproj) on the developer's computer - not a built version of the library so that changes and source code case easily be viewed when dealing code from this library.

This works quite well and would prefer to not have to switch to binary references (but will if this is the only solution).

The problem I have is that because of some of the functionality that was added onto the MVC1 based library (view engines, model binders etc) several of the sites reliant on these libraries need to stay on MVC1 until we have full evaluated and tested them on MVC2. I would prefer to not have to fork or have two copies on each dev machine.

So what I would like to be able to do is set a property group value in the referencing web application and have this read by the above mentions library with the caviat that when working directly on the library via its containing solution I would like to be able to control this via Configuration Manager by selecting a build type and that property overriding the build behavior of the solution (i.e. 'Debug - MVC1' vs 'Debug -MVC2') - I have this working via:

<Choose>
<When Condition=" '$(Configuration)|$(Platform)' == 'Release - MVC2|AnyCPU' Or '$(Configuration)|$(Platform)' == 'Debug - MVC2|AnyCPU'">
  <ItemGroup>
    <Reference Include="System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
    </Reference>
    <Reference Include="Microsoft.Web.Mvc, Version=1.0.0.0, Culture=neutral, processorArchitecture=MSIL">
      <SpecificVersion>False</SpecificVersion>
      <HintPath>..\Dependancies\Web\MVC2\Microsoft.Web.Mvc.dll</HintPath>
    </Reference>
  </ItemGroup>
</When>
<Otherwise>
  <ItemGroup>
    <Reference Include="System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
      <SpecificVersion>False</SpecificVersion>
      <HintPath>..\Dependancies\Web\MVC\System.Web.Mvc.dll</HintPath>
    </Reference>
  </ItemGroup>
</Otherwise>

The item that I am struggling with is the cross solution issue(solution TheWebsite references this project and needs to control which build property to use) that I have not found a way to work with that I think is a solid solution that enabled the build within visual studio to work as it has to date.

Other bits: we are using VS2008, Resharper, TeamCity for CI, SVN for source control.