How to assign Application name to profile function?

Hello
Trying to store additional information after membership create user. 
But when clicking store button page generating duplicated username with different application id and userid.
I've found solution. But couldnt understand how can i assign application name to profile function?
any help?
solution
"It is absolutely necessary to assign a name's app for the profile function properly. Since no name the system creates a name from the application automatically and there the reason for the creation of another ApplicationId."
My Codes
protected void AdditionalInfoClick(object sender, EventArgs e) { if (Session["UserName"] != null) { AccountProfile.CurrentUser.FirstName = Server.HtmlEncode(txtFirstName.Text ...