Moving file failed

Every time I launched my project the error display :
"Moving file failed
/Temp/…dll to Library/ScriptAssemblies/Assembly-CSharp-firstpass.dll failed:…

After i canceled all errors, and enter unity editor, in console errors show up:
Script compilation error: Couldn’t replace Library/ScriptAssemblies/Assembly-CSharp-firstpass.dll
Script compilation error: Couldn’t replace Library/ScriptAssemblies/Assembly-CSharp.dll
Script compilation error: Couldn’t replace Library/ScriptAssemblies/Assembly-CSharp-Editor.dll

Loading script assembly “Library/ScriptAssemblies/Assembly-CSharp-firstpass.dll” failed!
Loading script assembly “Library/ScriptAssemblies/Assembly-CSharp.dll” failed!
Loading script assembly “Library/ScriptAssemblies/Assembly-CSharp-Editor.dll” failed!

Any suggestion will be appreciated!

My guess is that your game has crashed in some weird way and it is still running and using these DLLs. When you try to build the game again the DLLs are in use and cannot be over-written. Perhaps try rebooting your machine. (Or, if you are comfortable, try and see if Task Manager or Activity Monitor show your game running, and kill off the process.)

I got this error once, the thing was that I was using dropbox to sync my files. Maybe if dropbox is using the file to upload you can’t manipulate it at the same time - So, if it’s the case you are using dropbox just wait for the file to be uploaded and it doesn’t take so long then hit on “Try Again” button.