I've installed the newly released version of Visual Studio 2017 and started a fresh ASP.NET Core project targeting .NET Core.
Out of the box, I'm getting the
The type or namespace name 'System' could not be found (are you
missing a using directive or an assembly reference?)
error. Any idea what's causing this and how to fix it?
Also, looks like there are problems with NuGet packages as well:
I also tried dotnet restore on the project through the command line and got the following error:
P.S. Kind of disheartening that you get an error in a fresh new project in the latest version of Visual Studio 2017!
UPDATE:
SDK version is v 1.0.1 -- see below:
UPDATE 2:
This is very strange. Looks like the original problem was due to NuGet package source pointing to a folder under Visual Studio 2015 folder. I unchecked it and left only nuget.org. With that my project seemed to have restored all the packages and when I started the project it loads up the standard ASP.NET page. But if I open startup.cs file, I get red squigglies all over the place but if I run the project, it works fine. What's going on here?
UPDATE 3:
I closed the project and VS 2017. I then restarted VS 2017 and opened the project and now it seems to be fine. And I'm not referencing the .NETStandard library 1.6.1 and everything seems to be working fine now.
I had the same issue in my Visual studio 2017 .Net Core application. I closed the Visual studio and re-open fixed everything.
Came across the same issue today. I had an old nuget source that no longer existed. So I went into Tools > Nuget Packet Manager and un-checked the wrong one. Hit "Ok", and then rebuilt the project, and it works great now. It seems like you stumbled onto it, but also wanted to verify that it fixed my issue, and it does.
I had the same problem, first when converting a VS2015 net core mvc web project to 2017 and then when trying to create a new core web application in 2017.
Went to Tools|NuGet Package Manager|Package Manager Settings - checked 'Allow NuGet to download missing packages' and 'Automatically check for missing packages during build in VS' and then clicked 'Clear All NuGet Cache(s)'.
Then re-built the solution - it found and loaded all the required packages and ran OK.
May not work for all cases but simple and worth a try.
Multiple closing and reopening of VS2017 fixed it for me.
I had the same issue, the solution for me was to clear the NuGet cache. Tools > NuGet Package Manager > Package Manager Settings > Clear All NuGet Cache(s)
Check the version .NET Command Line Tools in CMD, just type dotnet --info. If version is 1.0.0, then try to install latest version .NET Core SDK from here.
Find the broken project and right click, Unload, right click, Re-load. Fastest fix for me.
If you get the problem while using the CLI, try doing nuget restore instead of dotnet restore as that sometimes pulls down packages that the dotnet CLI seems to miss.
I have had the same issue with Visual Studio 2019 and .NET Core SDK 2.2.
These steps solved the problem:
Close the Visual Studio
Open the Visual Studio as Administrator
Open the Solution
Right click on Solution -> Restore NuGet Packages
I've tried all answers above. For me works only removal and adding the reference again described in the following steps:
Open 'References' under the project.
Right click on 'System' reference.
Click on 'Remove'.
Right click on 'References'.
Click 'Add Reference...'.
From right menu choose an 'Assemblies',
In a search field type 'System'.
Choose 'System' from the list.
Click 'Add' button.
IMPORTANT: Restart the Visual Studio.
'System' reference you can replace with any you need.
Try adding the following line above the other references in the csproj file
<Reference Include="netstandard" />
For me the problem was caused by my project having a custom IntermediateOutputPath. For some reason, if project_name.csproj.nuget.g.targets is not in obj subfolder of project folder, the error occurs.
Using default IntermediateOutputPath or keeping a shadow copy of project_name.csproj.nuget.g.targets in fake obj folder solves the problem for me.
This issue seems to be triggered by a myriad of reasons. Mine was caused by cloning directly from VSTS using Git Bash, my project directory had spaces in it. Git Bash changed those spaces in the path to %20. It was throwing off all the references in my project. So for anyone who tried everything else and are at their wits end, make sure %20 is not in the path.
So, I have cloned the repository from github and started getting this error.
It was my project uploaded from another machine. I later realized that I have used the materialdesign packages in my project.
I have uninstalled and reinstalled these packages and it fixed my issue.
Had the same problem. Uninstalled Application Insights from my projects using the nuget package manager. I'm not looking at that yet, I just wanted core and unit tests. Problem solved.
I also had the same problem.
The is no SDK folder under the Dependencies one. Therefore, no Microsoft.NetCore.App libraries !
To solve this problem, in Nuget manager window, install any nuget which depends on .NetCoreApp (you can install for example Microsoft.AspNetCore or BundlerMinifier.Core from the Microsoft Visual Studio Offline Packages source).
The SDK will be restored by the same time.
Once it is back, you can uninstall the previously added nuget. The SDK will remain in place.
Not quite sure in which order vs 2017 trying to resolve packages.
But my situation was following. In my VS2015 I had configured local and 3rd party source for nuget packages, newly installed version of 2017 loaded them too.
https://api.nuget.org/v3/index.json was first in list.
But vs2017 throwed an error that it can't restore .net core libraries from my another local repo.
After I unchecked all of them except https://api.nuget.org/v3/index.json, it had started to working normally.
I had this problem too, but not right now, this steps solved my problem: Choose Project -> Properties from the menu bar. In the Project properties window, under Configuration Properties -> General, make sure that Common Language Runtime Support is set to Common Language Runtime Support (/clr)
Simply opening the NuGet package manager and then the Visual Studio settings related to it - without changing anything - merely looking around, and when I closed out, the problem was gone.
This seems to be an intermittent issue that can come and go for no obvious reason.
None of the answers here worked for me so I'm posting what did work.
My errors were mostly the same as the original poster but I also had:
Error loading meta data for 'Microsoft.Extensions.FileProviders.Embedded.2.0.1'
hexadecimal value 0x1C invalid character
Every time I attempted to download a different nuget package or restore old packages I would see this error. I also saw the other errors such as:
type or namespace system could not be found
What worked for me:
opened the filepath that the error said the bad metadata was in, which for me was C:\Program Files\dotnet\sdk\NuGetFallbackFolder\microsoft.extensions.fileproviders.embedded\2.0.1
Then, I put the contents of that folder into another folder I named "hiding".
Then, I went back to the nuget package manager and tried to install a package, hoping to have the SDK restored. IOt worked successfully, and all my other errors were gone as well, and the fresh new project runs as it should!
The problem for me occurred when running my Visual Studio as Admin with a separate user-- I had created a Git Repo with the source files in the user documents of my normal account. When I created a new solution in that folder the above errors occurred. Try creating your project in a different place and see if the error still occurs.
I was facing the same issue when I created a new project (.net Core 2.2) in VS2019.In my case there was an Azure package which was creating the problem.I uninstalled it and the project started working fine.
Run mentioned below command to uninstall the package.
Uninstall-Package Microsoft.VisualStudio.Azure.Containers.Tools.Targets -Version 1.7.10
I had the same problem. I cloned a github project and this error came. So I deleted the cloned project and then I cloned the project again and it worked fine.
I have the same problem as described here:
https://github.com/NLua/NLua/issues/33
Though I have followed the instructions to create a console application...
http://www.screencast.com/t/M12TqePQxW
...which works just fine, when I create a library project and reference it from another project (in this case, a Web API project) the following error occurs:
Unable to load DLL 'lua52': The specified module could not be found.
At this line:
using (var lua = new Lua())
How can a library project be made with the NLua nuget package without failing?
It is the exact same issue as described in the GitHub issue, the Nuget package is missing two DLLs that you need to use lua52.dll. One small difference, the current package (version 1.3.2.1) includes a newer version of lua52.dll that was built with VS2013. And therefore has a dependency on msvcr120.dll and msvp120.dll.
Beware that this may change in the future when Nuget updates your project.
As-is, you need to download and install the Visual C++ redistributable package for VS2013. Run both vcredist_x64.exe and vcredist_x86.exe so your project can run either in 32-bit or 64-bit mode.
To avoid having to do this on the machine on which you want to deploy your program, I recommend you copy the two DLLs from the c:\windows\system32 (64-bit) or c:\windows\syswow64 (32-bit) directories into the same directory as your EXE.
The package author could have done a better job putting this package together. Short from including the DLLs in the package, the better solution would be for him to rebuild lua52.dll with the /MT option so these dependencies are linked in. Consider clicking the New Issue button to let him know.
I have a Team City Nuget build setup which works fine. However, I have tried to update some nuget packages, one of them being: Microsoft.AspNet.Mvc. This was updated from version 5.2.2 to 5.2.3.
This broke the build. Examining the logs I noticed that the nuget package restore seems like it didn't even try to install Mvc. However, the packages folder that was generated by Team City has a Microsoft.AspNet.Mvc.5.2.3 folder but there is no dll file in the lib folder.
I'm at a loss here I don't see why updating to different package version breaks nuget restore.
Any insights on this behavior? Thanks in advance.
Delete the "Microsoft.AspNet.Mvc.5.2.3" package folder completely. The NuGet restore action should recreate this folder and download the assembly or assemblies correctly which are supposed to be in the "lib".
I've got the exact same issue on my build server and that solved the issue.
Check all of your projects in the solution and make sure they're targeting the same version of the .NET Framework. I've seen this flip out a build server before.
Also check in your solution packages directory and make sure that all projects that contain references that are packages are listed in the repositories.config file, so that they all get restored properly on the build server.
Please bear with me on this, since I am a Java developer just dipping a toe into the ASP.Net world
I started coding in an existing C# VS2012 codebase. It uses nuget and Newtonsoft is mentioned in the packages.config
When I right-click on Controllers > Add a new controller, I get the following error.
Could not load file or assembly 'nunit.framework, Version=2.2.4.0, Culture=neutral, PublicKeyToken=...' or one of its dependencies.
The system cannot find the file specified.
Now looking around in Google, it seems the GAC is missing an NUnit assembly. Not sure what I should do about that. Should I get NUnit? Why is it looking for a certain version of nunit (& that too a very old one)?
Any help for me to resolve this problem will be highly appreciated!
When you click "Add new Controller' Visual Studio will try to complete the parse/build to populate a number of values in the window that it is supposed to show you (with the available Models and available Views). It looks like at least one of your projects is missing a dependency (probably your Unit Test project).
NUnit 2.2.4.0 is indeed a pretty old version, it doesn't even exist on NuGet yet (which would have been an easy fix). It makes sense that NUnit is not installed in the GAC, since you normally don't put everything in the GAC just because it seems to be possible. If you're willing to upgrade to the latest NUnit version, the easiest way is to add the NUnit NuGet package to your project through the Package Manager.
I would assume that when you'd open the project file for the project that is generating this warning in Notepad, you'd see a <hintpath> tag as a sibling of the NUnit Reference (it may not be there) which points to the folder where it is telling Visual Studio to look for NUnit.
I suggest you install the NUnit version your project is looking for from here and then update the reference in your project to point to the correct location. That should fix the issue.
As for your remark on the specific version, .NET Assemblies are compiled with a specific version number (usually set in the AssemblyInfo.cs) a reference in a project file can be to a specific version or to any assembly with that name (highlight the reference in the Solution Explorer and check the properties window (ctrl+w,p or alt+enter). You'll see a property "Specific Version" which in your case is set to "true" which caused Visual Studio to store the assembly version in the project file.
Add the code files into a workable solution project.
It is workable for me.
Or, try to create a new Nunit test project with the codes
I also try the following method, but not working for me
Install Nunit, adapter, SDK from the Nuget package
Clean-Rebuild
Thought I would try and get the most out of my visualstudio.com trial membership. I created a solution with a few projects, pushed it to the Microsoft git source control provider, configured a build definition and tried to build it on the project server. However it keeps failing telling me:
The type or namespace name 'Moq' could not be found (are you
missing a using directive or an assembly reference?)
I know this means that the build server can't find the Moq.dll library. I had installed it using NuGet, but configured my .gitignore to keep the packages folder out of source control. I also enabled NuGet package restore for the solution and pushed nuget.exe, nuget.targets, and nuget.config (all 3 of the files in the .nuget folder) along with all of the other project files.
Now I am sure I could get the build to work if I pushed the packages folder too, but I want to keep the nuget packages folder out of source control. So I am wondering, is this possible? The visualstudio.com docs say that the build servers have visual studio 2013 installed, and because of this I assume that nuget package restore would work to download the missing dll's so that they can be resolved by MSBuild. Is this right? Or to use automated CI builds at visualstudio.com, do you need to have your packages under source control?
According to the log file, nuget package restore downloaded the package. What gives?
Project "C:\a\src\MySln.sln" (1) is building
"C:\a\src\Tests\MySln.ProjA.UnitTests\MySln.ProjA.UnitTests.csproj"
(3) on node 1 (default targets). RestorePackages:
"C:\a\src.nuget\NuGet.exe" install
"C:\a\src\Tests\MySln.ProjA.UnitTests\packages.config" -source ""
-NonInteractive -RequireConsent -solutionDir "C:\a\src\ " Restoring NuGet packages... To prevent NuGet from downloading packages during
build, open the Visual Studio Options dialog, click on the Package
Manager node and uncheck 'Allow NuGet to download missing packages'.
All packages listed in packages.config are already installed.
PrepareForBuild: Creating directory "obj\Debug\".
ResolveAssemblyReferences: Primary reference "Moq". C:\Program Files
(x86)\MSBuild\12.0\bin\amd64\Microsoft.Common.CurrentVersion.targets(1635,5):
warning MSB3245: Could not resolve this reference. Could not locate
the assembly "Moq". Check to make sure the assembly exists on disk. If
this reference is required by your code, you may get compilation
errors.
[C:\a\src\Tests\MySln.ProjA.UnitTests\MySln.ProjA.UnitTests.csproj]
This line is also in the build log file, below the above:
Considered "..\packages\Moq.4.1.1311.0615\lib\net40\Moq.dll", but it didn't exist.
I had this same error but it was occurring on our build server. I had added Moq via NuGet, checked in the project and everything was fine. I then moved the project into a new folder in TFS and the build server just couldn't seem to find Moq. It was building great locally. I ended up fixing the problem by making sure all of my changes were checked into source control and then deleting my local source code directory. I got latest and my test project realized it needed a new copy of Moq. I blame TFS/ source safe or what ever the Visual Studio integration module is for not adding it to source control at some point in time.
Figured this one out on my own. Turns out I had added the nuget packages before moving the test project into a Tests subfolder. The solution still built on my LM, probably because the dependencies were already copied to bin/Debug. After reinstalling the nuget packages, the solution built on vs.com.