using declaration doesn't work

[gianmarialari]

Sorry for the trivial question.
When I try to execute this code

using var reader = new System.IO.StringReader("One\r\nTwo");

... inside a cell (Visual studio code 1.66.1), I get a "missing semicolon" error.

It's like you can't use the new syntax introduced in c# 8 for the "using" statement.
What am I missing?