Could not load file or assembly 'Microsoft.ServiceBus, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

I have been using this Microsoft.ServiceBus.dll recently in my .net windows service and it was working fine . Suddenly it started showing this error when being used in Windows service which is deployed now to production. Downgrading to 2.7.6 is not a solution as it is not working for me .

The file exists at proper place with proper reference given and Copy Local is also set to True.

.Please help