OK I try to re-formulate the problem I mentioned in #1018 (comment).

@forki Nice, thanks!

Ok I did some more tests and was really impressed to get NO error after specifying

Microsoft.AspNet.Razor

group Net40
 Microsoft.AspNet.Razor

group Razor4
 Microsoft.AspNet.Razor

in paket.references. I think what paket does is correct even considering that the resulting >csproj will not compile.

the first two are fine because one is net45-only and the other one is net40-only. But the third >one is net45 only as well.. This means I need some way to specify which one to take at build time >(I don't want to use two references to the same nuget package on a single compilation).

One suggestion would be to allow something like

group Main if NET45
 Microsoft.AspNet.Razor

group Net40
 Microsoft.AspNet.Razor

group Razor4 if RAZOR4
 Microsoft.AspNet.Razor

in paket.reference (or even paket.dependencies, not sure right now) and then add a condition >to the msbuild references like Condition="$(RAZOR4) == 'True':

<When Condition="$(RAZOR4) == 'True' And $(TargetFrameworkIdentifier) == '.NETFramework' >And ($(TargetFrameworkVersion) == 'v4.5' Or $(TargetFrameworkVersion) == 'v4.5.1' Or >$(TargetFrameworkVersion) == 'v4.5.2' Or $(TargetFrameworkVersion) == 'v4.5.3' Or >$(TargetFrameworkVersion) == 'v4.6')">

This is a feature request, but imho one that would make the group feature more useful.

Is this a scenario you want to tackle with the new group feature?

In RazorEngine we use 3 different builds for 3 different Razor versions

• Razor2 (last version supporting NET4.0)
• Razor3 (current stable)
• Razor4 (vnext, currently beta, used by some people for coreclr/ASP.net5 support)

We use conditional compilation to take care about the API differences and provide the same API on all 3 builds. The thing is that if we develop a new RazorEngine feature there is no reason to support only the latest when it will work fine on any Razor version. Handling 3 branches is not really an option either.

Now with the group feature I can compile for Razor2 and Razor3 because they target different frameworks.

Paket will generate a csproj file like this (this is simplified):

<Choose>
  <When Condition="$(TargetFrameworkVersion) == 'v4.5'">
     <ItemGroup>
      <Reference Include="System.Web.Razor">
        <HintPath>..\..\..\packages\Microsoft.AspNet.Razor\lib\net45\System.Web.Razor.dll</HintPath>
      </Reference>
    </ItemGroup>
  </When>
  <When Condition="$(TargetFrameworkVersion) == 'v4.0'">
     <ItemGroup>
      <Reference Include="System.Web.Razor">
        <HintPath>..\..\..\packages\net40\Microsoft.AspNet.Razor\lib\net45\System.Web.Razor.dll</HintPath>
        <Paket>True</Paket>
      </Reference>
    </ItemGroup>
  </When>
</Choose>

Which is perfect!

But I still can't add Razor4 to the mix, because the reference would be enabled the same time as Razor3 (when compiling for net45):

<Choose>
  <When Condition="$(TargetFrameworkVersion) == 'v4.5'">
       <ItemGroup>
        <Reference Include="Microsoft.AspNet.Razor">
          <HintPath>..\..\..\packages\razor4\Microsoft.AspNet.Razor\lib\net45\Microsoft.AspNet.Razor.dll</HintPath>
        </Reference>
      </ItemGroup>
  </When>
  <When Condition="$(TargetFrameworkVersion) == 'v4.5'">
     <ItemGroup>
      <Reference Include="System.Web.Razor">
        <HintPath>..\..\..\packages\Microsoft.AspNet.Razor\lib\net45\System.Web.Razor.dll</HintPath>
      </Reference>
    </ItemGroup>
  </When>
  <When Condition="$(TargetFrameworkVersion) == 'v4.0'">
     <ItemGroup>
      <Reference Include="System.Web.Razor">
        <HintPath>..\..\..\packages\net40\Microsoft.AspNet.Razor\lib\net45\System.Web.Razor.dll</HintPath>
      </Reference>
    </ItemGroup>
  </When>
</Choose>

Notice how TargetFrameworkVersion=v4.5 will now enable two System.Web.Razor.dll versions, which is not what I want, so I need some way to tell paket to generate an additional condition which should be true.

One way to solve this is adding a way to tell paket to add a group with a custom msbuild condition (see example syntax in from my earlier comment).

Just something to note: Groups already improve the situation as we don't need nuget.exe anymore to resolve Razor2 and Razor4 👍 . I still need to update all csproj files by hand, but at least I now have stable paths and can use paket update (of course I still need to set <paket>false</paket> for the Razor3 and Razor4 dependency).