>Hi everybody,
>
>I'm getting the following error trying to build a project in Windows 10:
>
>Severity Code Description Project File Line Suppression State
>Error Cannot register assembly "C:\_Siriusware\Main\Siriusware.Middleware\Siriusware.Middleware\bin\Debug\Siriusware.Middleware.dll" - access denied. Please make sure you're running the application as administrator. Access to the registry key 'HKEY_CLASSES_ROOT\Siriusware.Middleware.ErrorState' is denied. Siriusware.Middleware
>
>I know that I can fix it if I run VS as Admin. However, why do I need to run VS as Admin in order to just build the project?
>
>Thanks in advance.

The answer is in the error : Access to the registry key 'HKEY_CLASSES_ROOT\Siriusware.Middleware.ErrorState' is denied."

Writing to the registry requires elevated rights. If this is a COM assembly you could turn off the registration (which IAC only needs to be done if the interface changes). If you do need to re-register than use regasm or, as a one off, set the COM interop flag and run as Admin.