UWPはDisplayInformationを使用して画面サイズを取得する

        var displayInformation = DisplayInformation.GetForCurrentView();//
        var screenSize = new Size(displayInformation.ScreenWidthInRawPixels, displayInformation.ScreenHeightInRawPixels);        
        var resolutionScale = displayInformation.ResolutionScale.ToString();
        var resolutionScalevalue = Convert.ToDouble(Regex.Replace(resolutionScale, @"(^(" + "Scale" + ")" + (true ? "*" : "") + "|(" + "Percent" + ")" + (true ? "*" : "") + "$)", "")) / 100;          
        CurrentDisplayHeight = screenSize.Height / resolutionScalevalue;//    
        CurrentDisplayWidth = screenSize.Width / resolutionScalevalue ;    

window.Currentは、現在のappのサイズを取得します.

        ScrollViewer.Height = Window.Current.Bounds.Height - bootHeight -55;