Return Value

If the sign on information is not cached, the OAuth dialog popup will be displayed. This method should be called from within a QueuedTask or System.Threading.Task unless the caller is within ArcGIS.Desktop.Framework.Contracts.ConfigurationManager.OnApplicationInitializing in which case the main thread should be used.
Known issue: A thread check is not enforced.

Reference

ArcGISPortal Class
ArcGISPortal Members