Why do I get a warning icon when I add a reference to an MEF plugin project

Question

I wish to test the core class of a plugin by directly referencing the plugin project and instantiating the plugin class  When I create a test Console App project and add a project reference to the plugin project  I get a warning icon  yellow triangle with exclamation mark  next to the reference in the References list    When I instead add a reference to the dll  the assembly build output of the plugin  I get no such warning  What could this warning be trying to tell me

User · Answer

Try closing and opening VS    Seems silly but after 1 hour of following the above and finding everything lined up OK  I restarted VS 2017 and the problems were gone

User · Answer

For me  I ran into this issue when referencing a  NET Standard 2 0 class library in a  NET Framework 4 7 1 console application  Yes  the frameworks are different  but they are compatible   NET Standard is supposed to jive with both  NET Core and  NET Framework   I tried cleaning  rebuilding  removing and readding the project reference  etc    with no success  Finally  quitting Visual Studio and reopening resolved the issue

User · Answer

In Asp net core sometime it shows alert if you changes the project name space or name  To remove this kind of alerts you just Unload Project and load it again   If issue is still there means you it can not find your Assembly reference

User · Answer

Using Visual Studio 2019 with all projects targeting  Net Core 3 1 the solution was to    Clean   Build   Rebuild  Restart Visual Studio 2019

User · Answer

One of the reasons to get this annoying yellow triangle is that you are adding a reference to a project twice  meaning   Reference one  MyProjectOne  which contains already a reference to MyProjectTwo  Reference two  MyProjectTwo  By deleting the Reference two  the yellow triangle will disappear

User · Answer

To fix some not working stuff it has sense to remove some libraries sometimes  how would not that sound weird   Anyways  I believe the problem is too wide and might be caused by different factors  so want to share my situation solution   I had a project  brought by customer  with Xamarin Forms and Telerik libraries  The thing was in general related to the components  which libraries are not included into packages folder  nor available via Nuget  paid ones    The whole project References were  yellow   it looked horribly and scary   The solution was just to remove those Telerik references  including a few controls in code which were using that   Right after that all the references magically got their common normal grey color and the errors  mostly  disappeared    Mostly  - because  all red around  error messages about  the element is not defined anywhere  sometimes happen still  That s weird  and brings inconvenience  but I still able to compile and run the project s   just need to clean solution  restart Visual Studio  pray a little bit  clean again  remove obj bin folders  restart again  and it works well   The key thing is remove not available libraries references  as the error messages say absolutely another stuff   For instance  something like  Xamarin Build Download XamarinDownloadArchives not found or cannot find something  etc   but that just might mean you don t have some references available   Then remove packages folder  reload reopen the project solution  go to  Manage Nuget Packages  and click  Restore  button

User · Answer

In a multi-project solution  If every other thing failed    On the startUp project  check  Dependencies- Assemblies and see if the erring referenced project is there  Remove it and re-build

User · Answer

Make sure all versions are same for each projects click each projects and see the version here Project  gt  Properties  gt  Application  gt  Target  NET framework  a  Go to Tools  gt  Nuget Package Manager  gt  Package Manager Console Type Update-Package -Reinstall  if not working proceed to 2 b  b  THIS IS CRITICAL BUT THE BIGGEST POSSIBILITY THAT WILL WORK  Remove  lt  Target  gt  Maybe with multiple lines  lt   Target  gt  usually found at the bottom part of  csproj   Save  load and build the solution

User · Answer

Also happens if you explicitly reference a project that was already implicitly referenced  i e  project a references project b project c references project a  which adds implicit ref  Expand and see  project c references project b  you will see an exclamation mark next to b under project references

User · Answer

I also faced the same problem but my case was a bit different the ones above  I tried to open a project created in a different computer  I found that the path to package folder is not updated when you add a reference so restarting VS  changing  NET version  or any mentioned recommendation does not solve the problem  I opened the csproj file in notepad   and corrected all the relative paths to packages folder  Then  all the warnings are gone  Hope it helps

User · Answer

In Visual Studio 2019  one of my projects target framework was  net core but it was referencing another project whose target framework was  net standard  I changed all of the projects to reference  net standard and the icons went away  To see what your project is right click it and click properties and look at Target framework  You can also normal click the project itself and look at the  lt  TargetFramework   tag under  lt  PropertyGroup

User · Answer

I had created a new  sln which was put in a subfolder  The  nuget folder was missing from where that  sln file was added  Moving the  nuget folder from the root into the subfolder where my new  sln file was solved the issue for me  I came back later and added the  sln file to the root and deleted the subfolder  Doing this originally would have solved the issue as well

User · Answer

in VS 2017 Do a Clean then Build

User · Answer

For both of  or all of  the projects that you want to use together   Right click on the project   Properties   Application   Target  NET framework  Make sure that both of  or all of  your projects are using the same  NET framework version

User · Answer

I had these icons for a different reason  We have one big solution for all our projects  nearly 100   I made a subselection of the projects I was interested in and made a new solution  However the references where project references instead of references to the compiled dll s       After some research I found this link on GitHub which explains this is new behaviour in VS2015    On the GitHub page they explain a workaround for converting project references to binary references

User · Answer

As mentioned in the question s comments  differing  NET Framework versions between the projects can cause this  Check your new project s properties to ensure that a different default version isn t being used

User · Answer

Make sure you have the projects targeting the same framework version  Most of the times the reason would be that current project   where you are adding reference of another project   points to a different  net framework version than the rest ones

User · Answer

Reinstall all packages in all projects of the current solution   Update-Package -Reinstall

User · Answer

Check NETFramework of the referred dll  amp  the Project where you are adding the DLL  Ex   DLL         supportedRuntime version  v4 0  Project     supportedRuntime version  v3 0   You will get  warning icon  Solution   Make dll version consistence across

User · Answer

It s been a long time since this question was asked but if someone is still interested - I recently ran into similar icons  I was compiling a C  net project using VS 2008  I found VS could not locate the assemblies for those references  When I double clicked VS refreshed the references and removed the icons on some of those EDIT  which it could NOW locate   For remaining references  I had to compile the respective assemblies

User · Answer

Thank you all for the help  Here is a breakdown of how I fixed my problem   Right click on your project   Properties  Under Application change the target Framework  In my case ImageSharp was using  Net 4 6 1  You can find this in your packages config   Go to your project references  You ll notice SixLabors has a yellow triangle  You have to update the NuGet package   Right click on References   Manage NuGet Packages   Update SixLabors   You might have slight code updates  see below  but this fixed my problem   Convert ImageSharp Image to ImageSharp PixelFormats Rgba32

User · Answer

Encountered the same issue with a ASP Net Web App and two library class projects which needed to be referenced within the Web App   I had no information provided on why the build failed and the references were invalid   Solution was to ensure all projects had the same Target Framework   In Visual Studio 2015- Right Click project   Properties   Application   Target Framework  Save  Clean and Rebuild solution   The project references should no longer appear as yellow warnings and the solution will compile   My Web App was targeting  Net 4 5 whereas the other two dependent library class projects targeted  Net v4 5 2

User · Answer

Based on the answer from  AljohnYamaro  sorry  couldn t comment on your answer  new account without enough reputation yet  but upvotaded you   I ve checked the  csproj file  On my file  besides the standard project reference   lt ProjectReference Include  quot    ProjectA ProjectA csproj quot  gt       lt Private gt true lt  Private gt       lt CopyLocalSatelliteAssemblies gt true lt  CopyLocalSatelliteAssemblies gt   lt  ProjectReference gt   There were also a directy link to the compiled dll from the referenced project   lt ItemGroup gt       lt Reference Include  quot ProjectA quot  gt       lt HintPath gt    ProjectA bin Debug netcoreapp3 1 ProjectA dll lt  HintPath gt       lt  Reference gt   lt  ItemGroup gt   Removing this second reference solved the issue

User · Answer

Adding my 2 cents to the  kad81 answer   Go to Visual Studio -  BUILD -  Configuration Manager  In the  Active Solution Platform  drop down in top right hand corner  mine is VS 2012   if it is  Mixed Platforms   change it to the appropriate platform based upon your reference third party assemblies   Then in each of the project in the list  make sure you select same platform for all the project   if x86 not exist  then select     then you can select  x86     Rebuild the library projects first and then referencing projects   Hope this helps

User · Answer

I had the same issue in a solution with projects targting  NET Core 3 1   NET Standard 2 0 and  NET Framework 4 8  The issue was on this last one  The trick that solved the issue for me  was to change the target framework to  NET Framework 4 5  then back to  NET Framework 4 8  I have absolutely no idea why this fixed the issue  but it did  The IDE was Visual Studio 2019

[.net] Why do I get a warning icon when I add a reference to an MEF plugin project?

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