Calling ApplicationView.GetForCurrentView throws an error

Describe the bug

Calling ApplicationView.GetForCurrentView() in App.OnLaunched() throws this error:

System.Runtime.InteropServices.COMException: 'Element not found. (0x80070490)'

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Create a Blank, Packaged WinUI 3 C# app
2. Add the following code to beginning of the App.OnLaunched method in App.xaml.cs

ApplicationView.PreferredLaunchViewSize = new Size(500, 800);
ApplicationView.PreferredLaunchWindowingMode = ApplicationViewWindowingMode.PreferredLaunchViewSize;
ApplicationView.GetForCurrentView().SetPreferredMinSize(new Size(500, 800));

Expected behavior

App launches without an uncaught exception.

Version Info

NuGet package version: 3.0.0-preview1.200515.3

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
November 2019 Update (18363)	Yes
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Mobile
Xbox
Surface Hub
IoT

Additional context

This issue does not occur when using the non-WinUI C# Desktop App project template.

[asklar]

This is by design, all corewindow APIs are not supported in WinAppSDK. See https://docs.microsoft.com/windows/apps/desktop/modernize/desktop-to-uwp-supported-api#apis-that-have-dependencies-on-uwp-only-ui-features

[NPadrutt]

@Slion it looks like you would have to extend it yourself: https://docs.microsoft.com/en-us/windows/winui/api/microsoft.ui.xaml.window.extendscontentintotitlebar?view=winui-3.0