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.
My app keeps getting this error (I'm using VS 2013, VB.NET, and Windows 8.1, by the way):
Could not run the "GenerateResource" task because MSBuild could not create or connect to a task host with runtime "CLR2" and architecture "x86". Please ensure that (1) the requested runtime and/or architecture are available on the machine, and (2) that the required executable "C:\Program Files (x86)\MSBuild\12.0\bin\MSBuildTaskHost.exe" exists and can be run.
The app is for .NET 3.5 (3.5 and lower versions get me this error).
I try to run the app again. Sometimes, it works; sometimes, the error comes back.
I already tried looking up for answers at Google and the answer they gave me turned out to be: "Your build's username is too long" (they said that 20 characters or more cause the error), but it's not true. My user name is 5 characters only. Anyway, I don't think my build's username's length has anything to do with it; it makes no sense.
Does anyone know what is wrong with 3.5 and lower versions? Thank you.
This fixed the issue on my machine:
To resolve it, go to your csproj file and add the following line under the default property group:
<PropertyGroup>
...
<DisableOutOfProcTaskHost>true</DisableOutOfProcTaskHost>
</PropertyGroup>
Found here.
Clean and rebuild solution worked for me.
Adding this in each project is a cumbersome task. So you can set it in the environment variables.
Click Start>> Right-click Computer >> Properties >> Advanced system settings >> Click Environment Variables button to open the dialog, then under the System variables section, click New… button, type the Variable name = DISABLEOUTOFPROCTASKHOST, and type the Variable value = 1, then click Ok.
More here
I'm using VS 2013, VB.NET, and Windows 10, 64 bits, by the way
Just change in XML properites , Services : .NET Framework 4.6 instead .Net Framework 2.0 (Default)
and working fine for me.
I try adding the follow but didn't works
<PropertyGroup>
...
<DisableOutOfProcTaskHost>true</DisableOutOfProcTaskHost>
</PropertyGroup>
this solve this issue for me, adding the same as enviroment Variable
DisableOutOfProcTaskHost=true
I encountered this error when trying to build a sample solution that was included in some software that was installed under C:\Program Files\. Visual Studio prompted me to restart with elevated privileges (as it does when opening a solution in a "secure" location), however the build failed with the OP's error message.
Copying the solution to a "normal" folder (e.g. C:\Temp) solved it for me.
I tried opening an old VS2010 vb project inside VS2013 recently and just ran into this problem. I got around it this way:
I went to the vb project's properties page
I clicked the "Debug" tab
In the "Enable Debugers" section, I saw that the "(x) Enable the Visual Studio hosting process" checkbox was already checked.
I tried un-checking the "( ) Enable the Visual Studio hosting process" option
I saved these changes (Ctrl+S)
I then checked the "(x) Enable the Visual Studio hosting process" checkbox once more
I saved these changes (Ctrl+S)
My next re-build of the project was then successful.
Luckily, I was able to observe how the .vbproj file changed in my version control, and saw that it added the following line into it (which was not there before, despite the checkbox already being set initially):
<UseVSHostingProcess>true</UseVSHostingProcess>
None of the answers in this worked for me. I had to run Visual Studio as admin. Hope this helps someone in the future!
If you don't know how to run a program as admin on Windows, click this link.
I'm working with some application handed over by another person in which I must document the requirements, build and deploy processes.
The problem here is that Visual Studio (2005) is throwing a lot of errors since it can't find the references for the dlls.
This obviously won't let VS build the project.
Everything works fine on the persons computer but not on mine, even though the project references the same folder where the dlls are, the bin folder.
How can I circumvent these problems and get VS to properly reference the dlls?
The following printscreen shows the references screen for the project.
My guess is that your DLL uses a more recent .NET framework than your application does.
Check the properties for your DLL source (right-click on the DLL code in the solution explorer and choose Properties). Go to Application - Target .NET framework and compare the version to the one the application itself uses (right-click on the project code). Note: under your application properties check both the settings under Application - Target .NET framework AND under Publish - Prerequisites.
For what it's worth, even after changing the .vbproj file and removing many lines about hard coded values,
I eventually checked out the project again removed all references to the given DLL and then added it using the GUI.
Lesson learned, don't try to change out one DLL for a newer version without using VB2005 GUI.
The easiest solution will probably be to transfer everything to another project. It will be incredibly time consuming to find where visual studio has left the hard coded path at.
WOOT!!!! Compile the DLL file to a lower version of the .NET framework, and it will fix the problem!!!!
The paths in the project file cannot be the same or the assemblies referenced have a different version.
It might be worth unloading your project and the editing it to inspect where it's looking and for what version.
I had the same problem with an older Visual Studio Project that I opened in Visual Studio 2008. I tried to add new references to the project and got permanent errors that the dll's cannot be found. After the migration of the Project to Visual Studio 2010 I got the following error message when I tried to add a new reference:
'mySample.dll' or one of its dependencies, requires a later version of the .NET Framework than the one specified in the project. You can change ...
After changing the projects .NET Framework to a newer version everything works fine.
Good suggestions in other answers. In my case, it was because the libraries weren't copied (downloaded) successfully: the files existed, but were 0 kB.
Did a clean, which removed all the DLL's and then VS2008 complained it couldn't find the references (Duh!!!) and wouldn't rebuild....luckily I had and old version of the dll's and replaced them in the directory AND THEN did a rebuild to replace them...all references are now OK and we're back to normal....good old VS 2008
I just created a new VB Windows forms project using VS2010. The solution also contains a Fortran DLL project. I've set the platform to x86.
When I pull up the VB project properties it does not list the configuration or the Platform at the top of the properties dialog. This means I can't set the Compile tab Build output path differently for debug or release.
I've created several similar solutions using VS2008 and recently converted them to VS2010 and have not had this problem.
Mike
That is because you are using VS2010 Express and your single project is not in a solution project.
You could manually change the output from your .VBPROJ file with notepad. Inside that file you could do other changes . FOr exemple switching from Debug to Release. You have to restart your VS2010 Express edition to apply the changes (if I am not mistaken and it will be onkly true if you are using the Express Edition)
I build a C++ Builder 2010 project using Team City and noticed that I got issues when adding madExcept. The build complains about not finding MADEXCEPT.OBJ. My guess is that the standard include paths added in the C++ Builder 2010 IDE aren't propagated to the Team City build. Since the .cbproj files conatins no reference to where to locate madExcept the build fails. Am I right and how do I best rectify this? Building in the IDE on the Build Agent works fine and even using the RAD Studio Command Prompt, just when Team City is doing the build it fails. The thing that makes it extra strange is that there is no variable set when using RAD Studio Command Prompt that points to madExcept either, but it still works.
The issue seems to be that madExcept and the entire mad suite adds references to the include files and libraries to
HKEY_CURRENT_USER\SOFTWARE\Wow6432Node\CodeGear\BDS\7.0\...
Since the TeamCity build agent runs as another user this information is not available to it.