Q42.WinRT.Portable (nuget): This is the portable library that's compatible with WP, WinRT and .Net 4.5. It includes the DataLoader which functions as a wrapper around a Task<T> method. You can bind a progress bar to the DataLoader and show it as long as the task is running.
Keywords: phone|wp|wp8|winrt|metro|xaml|wpa81|c-sharp|dataloader|flyout|progressbar|universal-apps|uwp|windows-phone|windows10|xaml-winrt