"Consider app.config remapping of assembly ..." warning in F#

Question

After I installed VS11, I started to get the following error:

Consider app.config remapping of assembly "FSharp.Core, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" from Version "2.0.0.0" [C:\Program Files (x86)\Reference Assemblies\Microsoft\FSharp\2.0\Runtime\v2.0\FSharp.Core.dll] to Version "4.0.0.0" [C:\Program Files (x86)\Reference Assemblies\Microsoft\FSharp\2.0\Runtime\v4.0\FSharp.Core.dll] to solve conflict and get rid of warning. C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1490,5): warning MSB3247: Found conflicts between different versions of the same dependent assembly.

What exactly should I do? I have no idea how to do such a remapping.

Answer 1

Below is I think a sample app.config that does what is suggested. However, what is in your project, and what FSharp.Core reference is there? Are you targeting .Net 4.5 or 4.0 or what? Does this project reference some older F# library? This typically is because two projects reference different versions of FSharp.Core.dll, e.g. check the <Reference> nodes in the .fsproj files.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
          <assemblyIdentity name="FSharp.Core" publicKeyToken="b03f5f7f11d50a3a"
                            culture="neutral"/>
<!--      <bindingRedirect oldVersion="0.0.0.0-2.9.9.9" newVersion="4.3.0.0"/>  -->
          <bindingRedirect oldVersion="2.0.0.0" newVersion="4.0.0.0"/>
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

Answer 2

same error related to Json.Net

In project file I had

<Reference Include="Newtonsoft.Json, Version=6.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
   <SpecificVersion>False</SpecificVersion>
   <HintPath>..\packages\Newtonsoft.Json.6.0.1\lib\net45\Newtonsoft.Json.dll</HintPath>
</Reference>

and

<ItemGroup>
   <Reference Include="Newtonsoft.Json">
      <HintPath>..\packages\Newtonsoft.Json.5.0.6\lib\net45\Newtonsoft.Json.dll</HintPath>
   </Reference>
</ItemGroup>

Deleting the old one solved the problem.