HttpContext.Current.User.Identity.Name; not returning any

Hi,
I added blow in my web config.

 <membership defaultProvider="AspNetSqlMembershipProviderOffline">           <providers>               <clear/>               <add name="AspNetSqlMembershipProviderOffline" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ApplicationServicesOffline"                    enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" ...