When compiling your application under .NET Framework 4.0 in Visual Studio 2015, you may face the following warning:


warning MSB3275: The primary reference "DotNetBrowser, Version=1.x.x.0, Culture=neutral, PublicKeyToken=b0b5aaca9c95c84e, processorArchitecture=MSIL" could not be resolved because it has an indirect dependency on the assembly "Microsoft.VisualStudio.Shell.Immutable.10.0, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" which was built against the ".NETFramework,Version=v4.5" framework. This is a higher version than the currently targeted framework ".NETFramework,Version=v4.0".


Cause:

This issue is usually related to several versions of the .NET framework installed in the same environment.


Solution:

The simplest workaround is to edit the project file to ignore target framework version mismatches as follows:  


1. Unload the project by right clicking on it in Solution Explorer window and choosing Unload Project.  

2. Open the project file into the editor by right clicking on it in Solution Explorer window and choosing Edit projectname.csproj.  

3. Add the following element inside the <Project> element:


<PropertyGroup>  
    <ResolveAssemblyReferenceIgnoreTargetFrameworkAttributeVersionMismatch>
        true
    </ResolveAssemblyReferenceIgnoreTargetFrameworkAttributeVersionMismatch>  
</PropertyGroup> 

  

4. Save the project file.   

5. Right click on the modeling project in Solution Explorer and choose Reload Project.  


Source:

https://blogs.msdn.microsoft.com/visualstudioalm/2015/04/07/reference-could-not-be-resolved-error-when-validating-your-architecture-using-visual-studio-architecture-modeling-tools/