How to get users email?

Hello
I try to retrieve  the user's e-mail that he/she entered at registration. How should i write to get email adress, and view in in a label?
I tried this but it gives me error. 
protected void Page_Load(object sender, EventArgs e)
{
MembershipUser mu = Membership.GetUser();
string email = mu.Email;

lblEpost.Text = email;
} I found this link http://forums.asp.net/t/1258368.aspx But it did not solve my problem. I hope somebody can help me.
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