Try
Dim authTicket As FormsAuthenticationTicket = _
FormsAuthentication.Decrypt(authCookie.Value)
Dim roles = authTicket.UserData
Dim userIdentity As GenericIdentity = _
New GenericIdentity(authTicket.Name)
Dim userPrincipal As GenericPrincipal = _
New GenericPrincipal(userIdentity, roles)
Context.User = userPrincipal
Catch ex As Exception

End Try

Error 1 Value of type 'String' cannot be converted to '1-dimensional array of String'. C:\xxx