Why does the IEnumerable.Select() works in 1 of 2 cases ? Can not be inferred from usage

Question

I get this error message:

The type arguments for method \'System.Linq.Enumerable.Select(System.Collections.Generic.IE         


        

Answer 1

documentsOC.Add returns void.
It doesn't make any sense (and is impossible) to write .Select(...).

What you're trying to do cannot work in the first place; Select is lazy and doesn't call your function until you enumerate the results.

You should use a regular foreach loop.