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Visual studio 2019 go to definition and Intellisense not working

I have noticed a weird issue with Visual Studio 2019 v16.0.1 the IntelliSense about "Using directive is unnecessary" normally grey is missing and type reference suggestion for missing using is not working.
I also tried with Visual Studio 2019 Preview but no luck.
I have tried the following:
deleted .vs folder and restarted.
Reinstalled Visual Studio
Reset settings via import and export setting under tools
Any other suggestions will be appreciated.

Close Visual Studio
Delete .vs folder (it is a hidden folder inside the folder which contains the solution *.sln)
Start Visual Studio
Solved my problem
Update From the comments
Deleting Browse.VC.db file within .vs folder worked for me. I did this to avoid deleting .suo which has information I want to preserve
NOTE 1: I am using Visual Studio 2019, but it may work on other versions
NOTE 2: This did not solve the OP problem, but it is a good candidate to solve your

Go to Tools -> Options -> Text Editor -> All Languages -> General. Make sure “Auto List Members” is checked. Also, make sure “Parameter Information” is checked.

If you are facing this issue with Unity projects then,
Check in your Unity settings whether it has Visual Studio configured as the external editor.
Click on Regenarate project files in the Unity settings.
Go to Assets => Open C# project.
This will restart Visual Studio with your project.

In my case, Resharper is the culprit. Disabling it immediately solved the issue.

I think these issues are discussed here and are resolved by an update and some worksrounds are bring discussed:
https://developercommunity.visualstudio.com/content/problem/505489/cannot-navigate-to-the-symbol-under-the-caret-3.html

For anyone who are searching for another suggestion, I just go throught this issue, as OP said, I've deleted .vs folder, I've update vs to last version, I've uninstalled and reinstalled vs to the last version, I've reset settings, delete all obj folders, I've installed Microsoft.Net.Compilers but nothing worked, at the end I just remembered that sometimes the projects required WindowsBase library, until now I don't know why, but after adding that dll Intellisense started to function again.

I use resharper (vs 2017) but had not installed it on 2019. After installing Resharper on 2019 the intellisense started working again. (yes, it was working in 2019, then stopped)
I don't have an explanation on why this would fix it. Just did for me.

First time I use VS 2019, I need to manually install Code Analysis. Make sure it is installed at your project properties.
And today, for the new class, the suggestion or namespaces not showing for VS 2019 Intellisense, and Go to Definition not working too.
I must do close solution, and re-open and VS 2019 doing scanning while opening project, and then worked again.
I think this is bug for VS 2019. Try to close solution and re-open it.

I have tried almost all the solution mentioned above but it doesn't helped me. Trying to restart my PC solved my problem.

I tried lots of things but nothing worked for me until I found this post. He mentions a few things I have already tried that didn't work, but his final solution worked for me...
At the root of our solution there is a packages folder. I deleted the
entire contents of this folder. Upon reopening Visual Studio,
Intellisense and Go To Definition were restored to full working order.

close visual stdio
For mac in your folder: do command + shift+ .
you will see hidden files -> delete .vs folder
open solution again

After working for a few months, Intellisense suddenly stopped. This cost me a lot of lost time! I've been worked with Visual Studio for about 10 years, and this problem happens occasionally in every version.
Here's what I tried for this iteration of the problem:
Closing Visual Studio and re-opening does sometimes make the problem disappear for a short time, but it certainly doesn't solve it
Likewise restarting my laptop
Installing the latest Visual Studio 2019 update didn't help (I'm on 16.8.3 now if anyone's interested)
Deleting the hidden .vs folder doesn't seem to solve anything (doing so also means you lose your current window layout, as well as any bookmarks you've set)
Unticking the Track Changes option in this menu: Tools-> Options-> Text Editor-> General.
I've updated my NuGet reference to the Microsoft.Net.Compilers library to the latest stable version, as suggested here, but sadly this made no difference
I thought I've finally solved the problem by following the advice from Homer. I deleted the packages folder at the base level of my project (somewhat nervously, as I wasn't sure if it was needed), and thought it had solved the problem, but no such luck.
However, one thing to watch out for - after doing this, Visual Studio recognised my classes but no longer recognised built-in ones (all the referenced namespaces at the top of my controllers were underlined in red). I then deleted the .vs folder (again), which seemed to solve the problem.
When I recompiled my solution, it gave a few CS0433 compilation errors with duplicate namespaces for the MinLength and MaxLength directives in some identity user name and password validation code. I got round this by removing the Microsoft.EntityFramework Nuget library (I had to also remove Microsoft.AspNet.Identity.EntityFramework too, since this depended on it), then adding them both back in, making sure to include at least version 6.2 of the former (otherwise I got another runtime error to do with the FirstOrDefaultAsync method called somewhere!).
My current situation: all existing Intellisense is working, but it's not recognising new classes I add unless I exit Visual Studio and go back in again. May have to live with this ... unless anyone can help me?

I've got that problem today with only one project. I got no Intellisense warnings (i.e. naming styles, "Variable not referenced", etc..) for files in that project. Not in VS 2017 Pro nor in VS 2019 Community.
Check, if your Project->Build->"Warning level" is set to 0...

If you have Visual Studio 2017 installed side-by-side with Visual Studio 2019, close VS2019, open the project in VS2017, wait until it is fully loaded, then close VS2017, and reopen VS2019 - fixed!
There must be a bug in the VS2019 intellisense stuff, but VS2017 seems to fix it with no need to keep deleting the .vs directory.

"Could not launch Visual studio" error (on Mac)

I updated Visual Studio on Mac and after it tried to start, it told me I need to install Mono and directed me to a web page for that. I installed Mono. Now every time I launch Visual Studio, it just says
Could not launch Visual Studio
This application requires Xamarin.Mac native library side-by-side.
Please download and install the latest version of Mono.
I tried restarting but that didn't help.
What now?
(I'm running the latest macOS, and updated XCode if that matters. Mono is 5.4.0.201.)
New EDIT:(2022)
Users are saying there's a better way than uninstalling and reinstalling. I haven't tested it myself. See comments and answers for more information.
Previous EDIT:
Uninstalling and reinstalling is still the only way as the answer suggests, on: 2019:
March
July
August
September

The fastest and easiest way will be to uninstall and reinstall Visual Studio.

I have just ran into the same problem. I did follow the alert instructions and installed the newest mono framework from Mono websites (6.10.0). After this still the same issue. So I downloaded and ran VS4M installer and it said, it need version 6.8 of Mono framework and it did offer me to download and install this "update". So i went ahead. Still the same warning after launching VS.
Desperately enough after reading this thread I started looking for uninstall instructions (on official site). I did not want to use the script to auto-uninstall as I rather do it all by myself just for ensuring it will be everything done properly. So manual uninstall said to delete the Visual Studio app from /Application folder first. I did it. And woala: All the sudden the new app called "Visual Studio (old)" appeared (or maybe it was there already but I did not notice? Anyway, it was there). It was certainly weird, but I ran it. And it did work! Working instance of Visual Studio! I did check the updates and there was one for the app only. That was my first step straight after launching. It did download the new update and installed it correctly. Now I have end up with fully working and fully updated version of VS4M!
Conclusion:
Use VS4M installer to install all updates and necessarities to run VS4M. After this go to your /Application folder and delete "Visual Studio" app. The "Visual Studio (old)" app should appear. Run this app and update it straight away. (you might have to rename it afterwards from "Visual Studio (old)" to "Visual Studio")

Did you try going to the Applications folder? You'll see a Visual Studio.app file there and you can run Visual Studio by opening that.

I have sovled the problem by brew install --cask mono-mdk rather than brew install mono, in case anyone is installing mono through brew.

Error reported in web.config, but only when it is not open in the editor in Visual Studio Community 2015

I just changed to Visual Studio Community 2015 and I'm having a weird issue running a project. The project builds without any errors. But, when I go to start debugging I get the following error:
There is an error in web.config. Please correct before proceeding. (You might rename the current web.config and add a new one.)
This only happens if web.config is not open in the editor in Visual Studio. If I open web.config in Visual Studio and try to run the project, I am able to do so and no errors are reported.

Has anyone suggested that we close and reopen Visual Studio?

I had the same problem in a Web API project in VS Enterprise 2015. I knew there was nothing wrong with the Web.config file because, like you, all I had to do was to have it open before hitting F5. It went away after I removed and re-added the project to the solution during solution re-organizing. You might want to try that. No logics here but then the error seems illogical too.

I fixed/stopped the issue above and wanted to communicate what my fix was with the exact same symptoms as above. I had switched to a different published environment when this started happening (from UAT to Dev) and I commented out a section in the web.config file. Double checked to make sure I commented out the exact text. I even cleaned my solution and rebuilt it, same problem. Strangely, I could publish to the dev environment and the application would run (Web app with IIS 7).
The only difference between my local environment from when it was working and this problem was my web.config file. So I was thinking VS was having trouble accessing the file when not open in the IDE. I checked properties and the file had the appropriate settings. I then checked in the solution into our source code repository and the issue went away. We implement an SVN solution here.
Hope this helps.

Issue with running Unit Test in Visual Studio 2012

I am getting the following error while building unit-test.
Error: "IUnitTestStorage.Open should be called before operation can continue."
I have never got this error before and all was working fine before this moment.
I have tried deleting all bin and obj files and rebuillding, it didn't help. Moreover, when I created new unit-test project (with no code of mine) and it gives the same error.
Closing all Visual Studio instances and starting them back didn't help as well.
I am using Visual Studio 2012 Premium Update 4.

I just closed and re-opened VS2015 and cleaned solution and it worked for me

I got it today in Visual Studio 2015. Just delete all in debug folder, release folder and all in obj folder.
Build the solution then it works out.

According to this it helps to clean and rebuild solution, not just build. I know it's little bit silly but in case you haven't tried it...

It's an issue with Updated version of Telerik Test Studio. Try Re-installing Telerik Test Studio to Resolve this. It works for me.

Visual Studio 2012 csc.exe Error. Executable not valid for OS

I am getting the following error when trying to compile and test any type of project in Visual Studio 2012 Professional.
Error 1 The specified task executable "Csc.exe" could not be run. The
specified executable is not a valid application for this OS platform.
After testing multiple suggestions online nothing has fixed the problem. Anyone know what is causing this? Is there a new version of Csc.exe I need to get a hold of? I know this is the compiler just not sure what I need to do to fix the problem.

I had this exact problem today on my Win7 Machine. As Hans suggests, 'Navigate to C:\Windows\Microsoft.NET\Framework\v4.0.30319 and type "csc".'
The file may still exist but if you can open it with notepad, it will probably show just plain text of some errors. This is the indication that your compiler has been destroyed. At my office we have come up with a theory that a Windows update may be causing this because only a few machines have been affected, but I haven't read much online about it until now.
We fixed this by copying someone else's csc.exe into the C:\Windows\Microsoft.NET\Framework\v4.0.30319 directory and recompiling. Be sure to set the options on the file to read-only so this won't happen again. Good Luck!

The problems associated with csc.exe in Visual Studio 2012 can mostly be solved by repairing Visual Studio.
You need to repair Visual Studio. Go to Control Panel -> Programs. Then select your version of Visual Studio you are using and press "Change"(or right click it and press "Change"). When the setup appears, click "Repair".

I am on Visual Studio 2017 but this is the first google result that pops up for "csc.exe not found"
When I got this error I had to restart Visual Studio, being sure to select 'Run As Administrator'. Everything worked after that

I've faced this problem while i am trying to move Asp.Net Mvc Project from one computer to another ; error message was : The specified task executable location "c:\users\mypcname\documents\visual studio 2015\Projects\TestMVC\packages\Microsoft.Net.Compilers.1.0.0\build\..\tools\csc.exe" is invalid.
I solved this by
Creating new Mvc Project ;
going to that folder \Microsoft.Net.Compilers.1.0.0\build..\tools
and Copied the csc.exe file to my Projets >> \Microsoft.Net.Compilers.1.0.0\build..\tools\
i think when i was copying the project from the original Computer i left that csc.exe file in the specified folder.
Hope this will help someone.

Check your solution properties (right-click on Solution and select 'Properties') and make sure that the 'platform' field (Configuration Properties) is set correctly.

I think this problem is caused due to improper PC clean up. I was running Quick Heal PCTuner 3.0 software on a 64-bit windows 7 machine but suddenly due to loss of power my machine was shut down then when i opened it again I was getting this problem in VS 2013. Even TortoiseSVN checkout was not working and throwing internal error and something like corrupted disk also was shown when trying to delete some files on the harddisk.
I ran the PC Tuner again doing the Disk, Registry and traces clean up and it got fixed. maybe this problem may occur due to other cases also but is mostly related to the system's files In my case this is the fix
Regards.

in my case helped (I had .net framework 4.5.1 and vs c# 2010 express):
download the newest .net framework and run repair

On Visual Studio 2013, the same problem solved by doing this for me:
Right click the solution and open Configuration Manager. For the project(you may see at least one there), I've changed the Platform from Any CPU to x86 for the project that may causing the problem.

I've tried to delete and move csc.exe file but it doesn't do anything.
Then simply I upgrade .net version and than downgrade (returned to its original state) and it works.

I solved my problem by copying the whole folder containing my visual studio solution
From C:\Users\me\Google Drive...
To: C:\Users\me\OneDrive...