Your question is really bvery unclear so not sure if this will help. However, putting my babelfish in I think you mean how do I get a list of all sql server instances and log on to one just like the sql server logon dialog?
Well, look no more; it's all in here:
GNR8 - Simple C# Class Generator[
^]. Ignore the subject: there is a dialog and code in there to do what I think you need. If not, then feel free to ignore.