Why is R# reporting so many errors in my Typescript files when these files compile fine?

My Typescript files all show errors by R# but these compile and execute fine.

For example, I have an array and the array's push function or the length property show up in red.

For example, this is the error reported by R# for length: Symbol 'length' cannot be properly resolved, probably it is located in inaccessible module.
(btw, there's a missing 'an' before 'inaccessible')

Do I have a misconfiguration in R#? Why is it reporting all these errors which are not really errors?