Не работает выделение MonoDevelop / MonoDevelop selection does not work

Столкнулся с проблемой, MonoDevolop не выделяет многие встроенные функции и т.п. Он не о что их не выделяет, он их и подсказывать отказывается... Сначала я это игнорировал, пока все работало, но теперь он мне не выделяет Input и простейшая операция на скриншоте отказывается работать, когда я пытаюсь запустить пишет " `Input' does not contain a definition for `GetKey' ". Помогите решить проблему.

MonoDevolop doesn't allocate many built-in functions, etc. First time I ignored it while everything worked, but now it doesn't allocate Input and the simplest operation on the screenshot refuses to work when I try to start it writes " ` Input 'does not contain a definition for `GetKey ' ". Help solve the problem.

 

There are at least 2+ things that could have gone wrong.

Sometimes, the IDE will stop understanding Unity. To fix this, you have to "reload the solution"; which is sometimes a popup option, which is nice.. however, sometimes it's not.
If it's not, you can try to find "unload solution" then "reload solution" which can work.

After issue, I've noticed more so with Mono, is that if you have some bad syntax in your file, it stops auto complete (though, I'm not sure about saying it doesn't exist, like your example).

Sometimes, closing Mono & re-opening it works. (if the above does not).
Sometimes, closing Unity + Mono, then Re-opening Unity, then opening a file from in Unity fixes it.

For fixes beyond that, I see people with recommendations on certain files you can try to delete, however I do not remember their suggestions, so I will not try to write them for you

It is a nuisance, I know.