title: nunit locking dll
body: <p>I have been using nunit with visual studio 2010 on a windows 7 64-bit pc.</p>
  
  <p>I am able to open the nunit gui and run my unit tests.  If I then change one of the unit tests and try to rebuild, I am getting a file locking error as follows - </p>
  
  <blockquote>
    <p>Error 1   Unable to copy file "obj\Debug\myProject.Tests.dll" to
    "bin\Debug\myProject.Tests.dll". The process cannot access the file
    'bin\Debug\myProject.Tests.dll' because it is being used by another
    process.  myProject.Tests</p>
  </blockquote>
  
  <p>I have used process explorer to verify that it is the nunit-agent.exe that is locking the dll.</p>
  
  <p>I have noticed via tools > test assemblies that the nunit.exe is running under clr version Net 2.0 and nunit-agent.exe is running under clr version Net 4.0.  could that have something to do with the problem?  If so, how can I fix it?  If not, does anyone have any idea what else may be going on?</p>
  
  <p>Thanks for any thoughts.</p>