Retriving data from a irc server

Question

I have been creating a simple irc client that connects to a server and sends some simple commands to it

I have also figured out how to retrive data from the server by using streams

The problem is I have to run a never-ending while to keep retriving all the data from the server

I do it like this:
while ((inputLine = reader.ReadLine()) == null)
{
listBox1.Items.Add(reader.ReadLine());
}

The problem is that my form doesent respond (I cant use buttons, and such) since the while is never-ending

Is there any way of adding a event that triggers when there is new data from the server?

Here is my project:
dumpen.dk/include/files/IrcBot.rar

And a bonus question: When connecting to Quakenet and joining a channel it says: 451 Register first

Why is that?