The #using Directive


#using "[file:] filename "

#using <[file:] filename >

It is a fatal error (C1190) to have a #using directive and not build for managed code, i.e., with the /clr option.

The filename is enclosed in either double-quotes or angle-brackets (i.e., a less-than sign before and a greater-than sign after). The choice has a significance described below. A file: prefix is optional, but must follow the opening double-quote or angle-bracket immediately, i.e., with no white space. There may be any amount of white space, including none, before or after filename.