I have a multi-project solution with Prism Nuget packages installed in several projects. I then attempted to add a Prism Mef extensions package to one of the projects using the Nuget Package Manager UI (I have already added it to one of the other projects).
The first time I attempted to add the package, it failed to install one of the dependencies, no specific error reason, just "failed". So, I installed it a second time, all seemed to be fine, no errors reported, but a few of the references did not resolve.
So, I uninstalled the package and all dependencies and installed it again. Again all appeared fine, but more references do not resolve.
I have tried uninstalling and installing the package more times but get the same result every time now.
I have had this problem many times and I know its not specific to the Prism package as I've had it with loads of different packages.
I think its just a major bug with Nuget, but I'm hoping somebody will know an easy way to fix it. I think I usually have better success with the Nuget console, but I find it more effort to use.
I've done some searching online and not really found a good explanation of the cause of the problem or a way to resolve it.
Somebody at work completely refuses to have anything to do with Nuget as he has so many of these issues, but I am determined to make it work!
Within the Package Manager Console run the following command:
Update-Package -reinstall
This will reinstall each nuget package within that project which should resolve any missing references.
If you know you're missing a specific reference:
Update-Package -reinstall <Package-Name>
I just closed Visual Studio and reopened it and references are resolved...!
You need to follow this procedure.
1. Update-Package -reinstall
2. Restart visual studio.
You may want to check the .NET version of the package vs. your project.
I had an instance where my project was .NET 4.6.1, and the package I was attempting to install was using version 4.6.2. After updating my project to the same .NET version, the reference showed up.
I recently encountered this error on visual studio 2012, solution for me was to delete .nupkg file from nuget cache. Nuget cache location can be found from nuget settings > general > browse.
Note: I did not clear cache, I just deleted a specific file from cache directory and reinstalled the nuget package.
Delete all the <assemblyBinding> references from your .config file, then run this command from the Nuget Package Manager:
Get-Project -All | Add-BindingRedirect
This is how I fixed it.
I was working on a legacy .NET framework project (using <Reference Include... rather than PackageReference). The .dlls were referenced with a relative path that wasn't being resolved.
Fixed by changing to absolute paths, building, then changing back to the original relative paths.
For example:
<Reference Include="My.Package">
<HintPath>..\..\packages\My.Package.dll</HintPath>
</Reference>
Changed to:
<Reference Include="My.Package">
<HintPath>C:\Users\will\Documents\MySolution\packages\My.Package.dll</HintPath>
</Reference>
Then built and changed back to the relative path and the build still worked.
In our case, on one machine VS was holding onto an old version of a dependency, so references to newly added methods in the dependency were not resolving (even when package manager was reporting the latest version installed). The solution was to restart visual after uninstalling the dependency, then install again.
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?
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.
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
Make sure all versions are same for each projects click each projects and see the version here Project > Properties > Application > Target .NET framework
a. Go to Tools > Nuget Package Manager > 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 < Target > Maybe with multiple lines < /Target > usually found at the bottom part of .csproj.
Save, load and build the solution.
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.
Reinstall all packages in all projects of the current solution:
Update-Package -Reinstall
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.
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.
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.
Check NETFramework of the referred dll & 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.
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.
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.
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.
Using Visual Studio 2019 with all projects targeting .Net Core 3.1 the solution was to:
Clean / Build / Rebuild.
Restart Visual Studio 2019
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.
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.
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.
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.
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.
Open the YOURPROJECT.csproj file with a text editor then at the end of the file remove these lines inside the target tag, and then build the project again!
be sure the Package folder is in the correct path which mentioned in < Reference > < HintPath >
<Error Condition="!Exists('.......
Enjoy it ;)
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.
in VS 2017 Do a Clean then Build
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?
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 < TargetFramework > tag under < PropertyGroup >
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.
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:
<ProjectReference Include="..\ProjectA\ProjectA.csproj">
<Private>true</Private>
<CopyLocalSatelliteAssemblies>true</CopyLocalSatelliteAssemblies>
</ProjectReference>
There were also a directy link to the compiled dll from the referenced project:
<ItemGroup>
<Reference Include="ProjectA">
<HintPath>..\ProjectA\bin\Debug\netcoreapp3.1\ProjectA.dll</HintPath>
</Reference>
</ItemGroup>
Removing this second reference solved the issue.
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.
If you're using the newer style Sdk projects add OutputType to the ProjectGroup element with a value of Library in the project you're referencing.
It'll also give you grief if it's in the project you're referencing and it references a project without the setting.
find your .csprojc file and open it.
find your packages path. I fixed my project by this issue.
..\packages\EntityFramework.6.1.3\lib\net45\EntityFramework.dll
this .. means vs will find this dll in parent directory.
you should confirm your package path, and your will fixed this issue.
one more simple answer : exit visual studio and re-open it, it has solved for my problem.
I'm using a NuGet package called Hangfire in my VS project. However I'd like to be able to step thru each Hangfire API which is not possible as these files are under the "References" folder, so I've downloaded a copy of the Hangfire source code from Github. However, how do I integrate this code into an existing Visual Studios Project? Or maybe even simpler, instead of installing a NuGet Package, how do I reference the methods in the HangFire source code in my VS Project?
In order to reference these files, you'll need to...
Add the Hangfire project (or projects!) into your Solution. This can be done by right-click -> add existing Project on the solution.
Make sure that you're referencing the Hangfire in the Solution. This can be ensured by removing all references, and then readding them, making sure to draw from the Solution section in the Add Reference dialog.
Make sure the Hangfire projects are set to build in the dependant configurations. This can be done by selecting the Configuration Manager either in Solution settings or via the configuration or platform drop-down. Make sure the Hangfire projects are checked for any configuration/platform combinationin which your projects are selected
Assuming you have a repo for you project (and you always should), you may also be able to embed Hangfire as a subrepo in your repo, so updating and keeping versions synced is easier.
I have a VS2013 solution that has many projects all C# with framework 4.5
When I try and rebuild all projects in the solution I get an error message
This project cannot be viewed in the object browser because it is unavailable or not yet built
I note that in the start up project the references to the other DLLS appear as though the DLLs are missing.
I can actually get the solution to run by building each project one at a time, and then double clicking the reference in the start up project.
Eventually I have gotten rid of all the bad reference icons in the start up project and the solution will run.
However as soon as I rebuild the whole solution the bad references re-appear.
Strangely Build works, but Re-Build doesn't, and Clean and Re-build doesn't.
I do have the following set up.
Project Templates References Project DomainLayer
Project DataLayer References Project Templates and Project DomainLayer
Thus VS needs to build DomainLayer first then Templates then DataLayer.... perhaps it can't work this out?
What is going on?
Although you could build projects individually, but cannot rebuild solution. It sounds to be problem with target framework. Go to project properties and ensure you're targeting Framework 4.5 for all projects. Somewhere in some project this might be missing.
Try uninstalling the NuGet packages, ensuring all of the project references are removed, restarting VS, and installing the packages again. Afterwards, check that the references don't have any warning icons.
My only guess is that this happens due to some type of bug or due to manual modification of project files which causes VS to install and reference NuGet packages incorrectly.
I use vs2019 and have the same problem
My solution:
Upgrade .net framework
Close visual studio
Delete folder packages in solution
Open project again and rebuild solution
Hope useful for you.