ISubscriber on TFS 2015

I try write plugin for TFS 2015. 

I use "ISubscriber" 

public EventNotificationStatus ProcessEvent(TeamFoundationRequestContext requestContext, NotificationType notificationType,
      object notificationEventArgs, out int statusCode, out string statusMessage,
      out ExceptionPropertyCollection properties) {  statusCode = 0;
      statusMessage = string.Empty;
      properties = null;
      try {
        if (notificationType == NotificationType.Notification && notificationEventArgs is WorkItemChangedEvent) {
          var notification = notificationEventArgs as WorkItemChangedEvent;

          string projectName = notification.ChangedFields.StringFields.First(p => p.ReferenceName == "System.TeamProject").NewValue;
          var createdByDisplayName = notification.CoreFields.StringFields.First(p => p.ReferenceName == "System.CreatedBy").NewValue;
          var assignedByDisplayName = notification.CoreFields.StringFields.First(p => p.ReferenceName == "System.AssignedTo").NewValue;
string s = string.Format("{0} | {1}", notification.WorkItemTitle, notification.AreaPath);
  TeamFoundationApplicationCore.Log(string.Format(" WorkItemTitle | AreaPath : {0}", s), 1602, System.Diagnostics.EventLogEntryType.Information);
          TeamFoundationApplicationCore.Log(string.Format(" CreatedBy : {0}", createdByDisplayName), 1603, System.Diagnostics.EventLogEntryType.Information);
          TeamFoundationApplicationCore.Log(string.Format(" AssignedTo : {0}", assignedByDisplayName), 1603, System.Diagnostics.EventLogEntryType.Information);

 TeamFoundationLocationService service = requestContext.GetService<TeamFoundationLocationService>();
          Uri uri = service.GetSelfReferenceUri(requestContext, service.GetDefaultAccessMapping(requestContext));
          TfsTeamProjectCollection tfsTeamProjectCollection = new TfsTeamProjectCollection(uri); } catch (Exception ex) {
        TeamFoundationApplicationCore.Log(ex.Message, 1604, System.Diagnostics.EventLogEntryType.Error);
      }
      return EventNotificationStatus.ActionPermitted;
    }

I copy dll  to folder "C:\Program Files\Microsoft Team Foundation Server 14.0\Application Tier\Web Services\bin\Plugins"

After i create new User Story, i check in windows EventLog

Server install TFS 2015 RC (Server don't join Domain)

- CreatedBy : dongnt

- AssignedTo : Administrator 

Server install TFS Server 2015   (Server join Domain)

-  AssignedTo : |User 01%85c99e85-152f-46eb-a0b5-85b271fbee57|

why does it diffirence?  

TeamFoundationLocationService service = requestContext.GetService<TeamFoundationLocationService>(); <= service always null 

Can you help me ? :( I try many time but i ca'nt solve issue :(:(

Thanks you