You can use the System.Diagnostics.Process class, redirecting standard
output of one process and feeding that to the redirected standard input
of another.  In this case, you'd have two Process instances, one for
"dir" and one for "grep".

Note that "dir" isn't a program; it's a built-in command for cmd.exe.
So you'll need to specify "cmd.exe" as the actual executable for the
"dir" process, with the appropriate switches to execute the "dir" command.

Another note: I don't have first-hand experience using a program like
"grep" in this way, where the program reads to the end of the stream.
I'm pretty sure you just close the redirected input stream, but you
might have to experiment a bit to find out the exact technique, if that
assumption isn't correct.

Pete

Have a look at PowerShell - it's all about that kind of thing.