File is locked by Visual Studio 2019

Question

I have a weird problem in Visual Studio:

if an unhandled exception is thrown during the debugging process I'm not able to build my C# application:

Unable to copy file "C:\Projects\A\bin\A.dll" to "..\..\bin\A.dll". 
  The process cannot access the file '..\..\bin\A.dll' because it is being used 
  by another process.

Could not copy "C:\Projects\A\bin\A.dll" to "..\..\bin\A.dll". 
  Exceeded retry count of 10. Failed. 
  The file is locked by: "Microsoft Visual Studio 2019 (14904)"

Is there a permanent solution to solve this strange error? (my only workaround is currently to restart Visual Studio)

What I tried and not worked for me:

VS menu -> Tools -> Options -> Projects and Solution -> Build and Run -> and "set maximum number of parallel builds" to 1.
Stop AntiVirus
Enable Application experience service (not found in Windows 10)
untick VS menu -> Tools -> Options -> Projects and Solution -> General -> Allow parallel project initialization
untick Debug -> Options -> Debugging -> General -> Break all processes when one process breaks

It's also not practical to insert Pre-build event scripts in all of my projects! Link: https://blog.ndepend.com/visual-studio-script-saves-time-pain/

Does anyone have a solution to this problem?

The file is locked by Visual Studio, are you creating analyzers, components, anything that would make Visual Studio load your assembly, as opposed to just loading the source code? — Lasse V. Karlsen, Jul 03 '19 at 11:42
@LasseVågsætherKarlsen No. This problem only occur when an unhandled exception is thrown, otherwise I can build normally! (see my question) — leon22, Jul 04 '19 at 05:30

score 22 · Answer 1 · answered Oct 14 '19 at 15:05

22

What worked for me - Close the Solution, Delete the bin and obj folder, re-open and build.

answered Oct 14 '19 at 15:05

Riaan Mastenbroek

221
2
2

4

I find that just restarting VS is sufficient. – StayOnTarget Oct 29 '20 at 15:30
Thanks, deleting bin and obj folder worked for me. – Ivan Jul 18 '21 at 21:16

score 6 · Accepted Answer · edited Oct 29 '20 at 15:30

6

It's a little bit weird but the problem was caused by the Debug option Use Managed Compatibility Mode! So just untick Debug -> Options -> Use Managed Compatibility Mode and no more files locked errors by Visual Studio!

Remark: The downside of disabling this option is you will get annoying long time consuming evaluation errors by VS! (More information)

edited Oct 29 '20 at 15:30

StayOnTarget

11,743
10
52
81

answered Jul 22 '19 at 07:10

leon22

5,280
19
62
100

I think there must be a different root cause, as it doesn't really make sense that that option causes the effect. – cjb110 Jul 22 '19 at 07:14
@cjb110 I also think so, but in the meanwhile I can live with it! – leon22 Jul 22 '19 at 07:17
1

Enabling "Just my code" did the trick of solving your remark in my case. – Sander Oct 30 '19 at 15:04

score 2 · Answer 3 · answered Jul 24 '20 at 07:50

2

Deleting the obj and bin folders were impossible for me, so i had to install Microsoft's Process Explorer to find the application's dll process still running. Killing this process worked for me.

answered Jul 24 '20 at 07:50

Aribo Oluwatoba

86
5

this solution worked for me. Thank you for introducing me to Microsoft's Process Explorer software. I dowanloaded here [Download Process Explorer (2.5 MB)](https://learn.microsoft.com/en-us/sysinternals/downloads/process-explorer) – Ram Fattah Jan 25 '22 at 22:30
Glad you found it useful! – Aribo Oluwatoba Jan 27 '22 at 04:08
Same. In Task Manager I had to kill the process "NET Host" and then I could delete the obj/bin folders. – Christopher Aug 05 '22 at 14:28

Mohammad reza hedayat nia · Answer 4 · 2020-11-07T08:21:11.087

0

it is a little stupid but: In windows task manager in Process tab, just find Microsoft visual studio <2019>, click "^" to collapse it's child's tree and find "Microsoft Visual Studio XAML Designer" select "Microsoft Visual Studio XAML Designer" and simply end process it before every debug.

edited Nov 07 '20 at 08:21

answered Nov 07 '20 at 08:16

Mohammad reza hedayat nia

251
2
6

score 0 · Answer 5 · answered Jan 04 '21 at 09:42

0

Deleting was impossible for me but it turned out that VS2019 kept a debug version of the software running that didn't close automatically when I stopped debugging. In Task manager -> close the running app and I could start the build/debug again.

answered Jan 04 '21 at 09:42

Erik Thysell

1,160
1
14
31

PolicyWatcher · Answer 6 · 2021-04-23T16:30:42.323

0

I have encountered this in a WinForms project in VS2019, where none of the other suggested solutions has worked, and where exiting VS and attempting to delete the affected files was refused by the O/S still claiming the files were open.

The fix that has worked here in this case was to go to Task Manager, and to find and terminate a copy of VBCSCompiler that is being left running even after VS has terminated. It shows up under "Background Processes".

After that, starting VS again worked fine.

edited Apr 23 '21 at 16:30

answered Apr 22 '21 at 14:26

PolicyWatcher

447
2
5

This post doesn't look like an attempt to answer this question. Every post here is expected to be an explicit attempt to *answer* this question; if you have a critique or need a clarification of the question or another answer, you can [post a comment](/help/privileges/comment) (like this one) directly below it. Please remove this answer and create either a comment or a new question. See: [Ask questions, get answers, no distractions](/tour). – Paul Roub Apr 22 '21 at 14:35

score 0 · Answer 7 · answered May 24 '22 at 18:33

0

Deleting worked for me as well but only after I force exited the DTSDebugHost from taskmgr for any others that couldn't get it to work.

answered May 24 '22 at 18:33

TStewartFan

17
1
6

score 0 · Answer 8 · answered Mar 10 '23 at 09:49

I faced the same and it happened because the bash window that open after run, I did not close it, just minimized it, and it was still running. So when I again tried to run the program, it showed me that the file is locked by another process, and in my case it was obvious that I needed to exit the previously opened bash window.

Apart from trying the other work arounds, just check this one as well.

score -1 · Answer 9 · answered Oct 19 '21 at 22:38

-1

Run Clean before Building or use Rebuild option. VS will build it fine. Bit slow , but it works everytime. No VS restart required.

answered Oct 19 '21 at 22:38

Amrender singh

7
1

Clean build is not the solution. – Václav Švára Nov 16 '22 at 12:13

score -2 · Answer 10 · answered Jun 07 '21 at 18:34

-2

Simple fix in my case. I already had my application running when I tried to run it again and got this error. Closing it solved my problem.

answered Jun 07 '21 at 18:34

Metcalfe

61
6

File is locked by Visual Studio 2019

10 Answers10