Activities of "rafael sotelo"

Hi I'm using azure active directory for my WebApp, the user id is GUID given automatically by azure active directory, so im having problems with this code:

public long? UserId { get { var userId = Thread.CurrentPrincipal.Identity.GetUserId(); if (string.IsNullOrEmpty(userId)) { return null; }

            return Convert.ToInt64(userId);

Exception Details: System.FormatException: Input string was not in a correct format.

What can i do ?