Why would a non-UI class know how to update a UI class? I'd expect each
of the UI classes to know how to update itself based on a particular
method call.

Consider making the forms implement an interface so that something
(whether the app or the Serial class) can make calls not caring which
of the implementations it's talking to.

This isn't about being "new to C#".  It's about being clear when you  
communicate.  You write "no problem", but I'm not sure you mean that (or  
even that you understand that by writing that, you are implying that you  
agree to take more care with your posts in the future).

The post with which you started this thread and to which I replied did not  
even have a question in it.  It is possible to try to make an inference as  
to the question, but frankly...if a person cannot even be bothered to ask  
an actual question, I really don't see why I or anyone else should put any  
effort into trying to answer the question they didn't even ask.

Those of us who answer questions (and this may one day include yourself)  
do often try to make inferences and decode a person's post, to try to  
offer an answer in spite of a vague, ambiguous message.  But that doesn't  
mean we enjoy that, and it doesn't mean we're going to do it every time.

This is especially the case when one person starts developing a reputation  
of posting messages that require that extra work.  That person will find  
it harder and harder to get an answer as they continue to abuse the  
willingness of people to try to figure out what they really mean.

To some extent, if you are not sure what to post, then maybe you shouldn't  
post anything.  Wait until you _are_ sure of what to post.

It's not a problem if you don't know the specific C# jargon or idioms.  
But it is a problem if you cannot describe what you're trying to  
accomplish clearly, or if you don't even include a question in your post.  
Nothing that I'm talking about cannot be fixed by you simply taking some  
more time when you compose your post, putting some thought into whether  
and how the post actually expresses what you're trying to express.

Try to put yourself in the place of the person reading your post.  
Understand that we aren't mind readers and the only information we have  
available is that which you put as text in your post.  Try reading some of  
your recent posts and see if you really believe that they clearly express  
whatever question it is you're trying to ask.  If you perform that  
analysis honestly, you'll find that they don't.

Pete