anchor.diff:              | Net40 ->  Some TargetDotNetFrameworkVersion.Version40
               | Net45 ->  Some TargetDotNetFrameworkVersion.Version45
               | Net451 -> Some TargetDotNetFrameworkVersion.Version451
  +#if MSBUILD_AT_LEAST_14
               //| Net452 -> Some TargetDotNetFrameworkVersion.Version452 // not available in Dev15 MSBuild version
               | Net46 -> Some TargetDotNetFrameworkVersion.Version46
               | Net461 -> Some TargetDotNetFrameworkVersion.Version461
  +#endif
               | _ -> assert false; None
           match v with
           | Some v -> 
  
positive.code:     //[<Literal>]    
      //let private Net452 = "v4.5.2" // not available in Dev15 MSBuild version
  
      [<Literal>]    
      let private Net46 = "v4.6"
  
      [<Literal>]    
      let private Net461 = "v4.6.1"
  
      /// Get the path to the .NET Framework implementation assemblies by using ToolLocationHelper.GetPathToDotNetFramework.
      /// This is only used to specify the "last resort" path for assembly resolution.
  
negative.code: 
      /// Use MSBuild to determine the version of the highest installed framework.
      let HighestInstalledNetFrameworkVersionMajorMinor() =
  #if MSBUILD_AT_LEAST_14
          if box (ToolLocationHelper.GetPathToDotNetFramework(TargetDotNetFrameworkVersion.Version461)) <> null then 4, Net461
          elif box (ToolLocationHelper.GetPathToDotNetFramework(TargetDotNetFrameworkVersion.Version46)) <> null then 4, Net46
          // 4.5.2 enumeration is not available in Dev15 MSBuild version
          //elif box (ToolLocationHelper.GetPathToDotNetFramework(TargetDotNetFrameworkVersion.Version452)) <> null then 4, Net452 
          elif box (ToolLocationHelper.GetPathToDotNetFramework(TargetDotNetFrameworkVersion.Version451)) <> null then 4, Net451 
  #else
          if box (ToolLocationHelper.GetPathToDotNetFramework(TargetDotNetFrameworkVersion.Version451)) <> null then 4, Net451 
  #endif
          elif box (ToolLocationHelper.GetPathToDotNetFramework(TargetDotNetFrameworkVersion.Version45)) <> null then 4, Net45 
          else 4, Net40 // version is 4.0 assumed since this code is running. 
  
  