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Update: A sample project reproducing this bug can be found here at Microsoft Connect. I have also tested and verified that the solution given in the accepted answer below works on that sample project. If this solution doesn't work for you, you are probably having a different issue (which belongs in a separate question).
This is a question asked before, both here on Stack Overflow and other places, but none of the suggestions I've found this far has helped me, so I just have to try asking a new question.
Scenario: I have a simple Windows Forms application (C#, .NET 4.0, Visual Studio 2010). It has a couple of base forms that most other forms inherit from, it uses Entity Framework (and POCO classes) for database access. Nothing fancy, no multi-threading or anything.
Problem: All was fine for a while. Then, all out of the blue, Visual Studio failed to build when I was about to launch the application. I got the warning "Unable to delete file '...bin\Debug\[ProjectName].exe'. Access to the path '...bin\Debug\[ProjectName].exe' is denied." and the error "Unable to copy file 'obj\x86\Debug\[ProjectName].exe' to 'bin\Debug\[ProjectName].exe'. The process cannot access the file 'bin\Debug\[ProjectName].exe' because it is being used by another process." (I get both the warning and the error when running Rebuild, but only the error when running Build - don't think that is relevant?)
I understand perfectly fine what the warning and error message says: Visual Studio is obviously trying to overwrite the exe-file while it the same time has a lock on it for some reason. However, this doesn't help me find a solution to the problem... The only thing I've found working is to shut down Visual Studio and start it again. Building and launching then works, untill I make a change in some of the forms, then I have the same problem again and have to restart... Quite frustrating!
As I mentioned above, this seems to be a known problem, so there are lots of suggested solutions. I'll just list what I've already tried here, so people know what to skip:
- Creating a new clean solution and just copy the files from the old solution.
Adding the following to the following to the project's pre-build event:
if exist "$(TargetPath).locked" del "$(TargetPath).locked" if not exist "$(TargetPath).locked" if exist "$(TargetPath)" move "$(TargetPath)" "$(TargetPath).locked"Adding the following to the project properties (.csproj file):
<GenerateResourceNeverLockTypeAssemblies>true</GenerateResourceNeverLockTypeAssemblies>
However, none of them worked for me, so you can probably see why I'm starting to get a bit frustrated. I don't know where else to look, so I hope somebody has something to give me! Is this a bug in VS, and if so is there a patch? Or has I done something wrong, do I have a circular reference or similar, and if so how could I find out?
Any suggestions are highly appreciated :)
Update: As mentioned in comment below, I've also checked using Process Explorer that it actually is Visual Studio that is locking the file.
This is going to sound stupid, but I tried all these solutions, running VS2010 on Windows 7. None of them worked except the renaming and building, which was VERY tedious to say the least. Eventually, I tracked down the culprit, and I find it hard to believe. But I was using the following code in AssemblyInfo.cs...
This is pretty common, but for some reason, changing the version to 2.0.0.0 made things work again. I don't know if it's a Windows 7 specific thing (I've only been using it for 3-4 weeks), or if it's random, or what, but it fixed it for me. I'm guessing that VS was keeping a handle on each file it generated, so it would know how to increment things? I'm really not sure and have never seen this happen before. But if someone else out there is also pulling their hair out, give it a try.
When I have come across this problem it is to do with the Fact that the project I am trying to build is set as the Startup project in the solution making the .exe in the obj folder locked ( it also appears in your task manager,) right click another project in your solution and choose set startup project. This will release the lock, remove it from task manager and should let you build.
Using Visual Studio I could never come up with a simple project to reproduce the error.
My solution was to disable the Visual Studio Hosting process.
For those interested I have attached a handle trace for the offending handle:
For Windows Services using WCF, I ended the WFC host process and it worked. I hate it when this happens, and it happens randomly at times.
I know this is a very old question, but I recently experienced the "cannot copy from obj to bin" error in VS 2012. Every single time I tried to rebuild a certain project, I got the message. The only solution was to do a clean before every rebuild.
After much investigating, it turns out I had an incomplete pragma warning statement in one of my files that did not prevent the compilation from succeeding, but was somehow confusing VS into keeping the file(s) locked.
In my case, I had the following at the top of the file:
That's it. I guess I was attempting to do something a while back and got distracted and never finished the process, but the VS warnings about that particular line were lost in the shuffle. Eventually I noticed the warning, removed the line, and rebuild works every time since then.
I have the same problem (MSB3021) with WPF project in VS2008 (on Windows 7 x32). The problem appearing if i try to re-run application too quick after previous run. After a few minutes exe-file unlocked by itself and i can re-run application again. But such a long pause angers me. The only thing that really helped me was running VS as Administrator.