解决编译报错：Unable to copy file， because it is being used by another process.

Error    63    Unable to copy file "D:\DEV\XXX Website\trunk Source Code\Common\WebControls\bin\Debug\WebControls.dll" to "bin\WebControls.dll". The process cannot access the file 'bin\WebControls.dll' because it is being used by another process.   XXX.WebError    63    Unable to copy file "D:\DEV\XXX