c# - .NET Unity suddenly stopped working : "The type name or alias x could not be resolved" -

in 1 of 8 projects in our solution have package.config file list of class/controls etc.. register unity e.g :

<register       type="com.sample.example.class, com.sample.example"       mapto="com.sample.example.class, com.sample.example"       lifetime="instance" /> 

i making changes , added new class register got error: "the type name or alias x not resolved" if fine, had missed configuration.

however error, no matter what, every class in config file. have reverted changes, deleted , re cloned application , re installed visual studio still same error. cannot understand why doesn't work now. code same used , has been working ~5 years.

other changes made @ time (but have since reverted, deleted etc..):

1. added reference microsoft.csharp
2. added microsoft.office.interop.outlook nuget package, use in other projects in solution. said i've reset code anyway these aren't here now.

any massively appreciated blocked developing!!!!