Have a look at the login page design here:
Traditional Login page design discussion[
^]
Login Controls were released by Microsoft from ASP.NET 2.0, have a look at them
here[
^].
For, building Login Page using Login control, look:
How to: Create an ASP.NET Login Page[
^]
ASP.NET Login Controls Overview[
^]
How to add a Login, Roles and Profile system to an ASP.NET 2.0 [
^]
Now, for your exact case, if you want to stick with it then you can use
Session
(one of the state management technique). Store the logged in username after login and use the session later to show it whenever and wherever needed.