Hmmm,
I have never touched C#, being a true Linux fan and as
such prefering C++ ... but I can understand what you are
trying to do.
What I don't understand is WHY you are trying to do it.
Connecting to an Irc server is amazingly easy, being
a simple text based protocol, no encryption or authentication
or anything as such, it would only take a few lines of code
to establish a connection, and very little code to send
and recieve messages, whereass sending lines to a
running process is slow, akward, glitchy... and harder
to program.
If you really must use Mirc though... why not use its
pluggin capabilities and write a DLL. Or if that dosn't
tickle your fancy write a small go-between script
using the build in scripting language.
Anyway, Enough Babbling From Me!
PS: .net should die, and Microshaft should burn in the fires of hell.