how to check weither aspnet profile variable is set OR not?

[Hansaor]

I am using asnet membership.There is a role named member. In root there is a site-visitor page, on that page in page load I want to check whether member is logged-In or not i.e. profile variable has set OR not.How can I check that?I gave search on google as well but failed to get correct answer.i am setting profile like -\[code\] HttpContext.Current.Profile.SetPropertyValue("UserName", UserName);\[/code\]