To follow along with the examples in this chapter, the following software is required:

• Windows 10 version 1809 or later or Windows 11. You can find your version of Windows in Settings | About.
• Visual Studio 2022 version 17.0 or later with the following workload: .NET Desktop Development. On the Installation details tab of the Visual Studio Installer, ensure that Windows App SDK C# Templates is selected.

The source code for this chapter is available on GitHub at this URL: https://github.com/PacktPublishing/Learn-WinUI-3-Second-Edition/tree/main/Chapter01.

Note

The Windows App SDK site on Microsoft Learn has up-to-date guidance on setting up a developer workstation for WinUI 3 development: https://learn.microsoft.com/windows/apps/windows-app-sdk/set-up-your-development-environment.

Before UWP applications were launched with Windows 10 in 2015, there were XAML applications for Windows 8 and 8.1. The XAML syntax and many of the application programming interfaces (APIs) were the same, and they were Microsoft’s next step to achieve universal app development across desktop, mobile, and other platforms (Xbox, mixed reality, and so on). A XAML app could be written for Windows 8 and Windows Phone. These projects would generate separate sets of binaries that could be installed on a PC or a Windows Phone.

These apps had many other limitations that modern UWP apps do not. For instance, they only ran full-screen, as shown in the following screenshot:

Figure 1.1 – Windows 8 full-screen app (sourced from Stack Overflow; reproduced under CC BY-SA 4.0 – https://creativecommons.org/licenses/by-sa/4.0/)

Many other early restrictions on Windows 8 apps have been lessened or completely...

While taking a leap forward with the launch of Windows 10, Microsoft also blended the best of what worked in previous versions of Windows. It brought back the start menu, but its contents look an awful lot like the Windows 8 home screen experience. In addition to an alphabetized list of all installed apps, there is a resizable area for pinned app tiles. In fact, when running Windows in Tablet mode, the start menu can transform into the Windows 8-style home screen experience for better usability on a touchscreen.

When Microsoft launched Windows 10, it also introduced UWP applications to Windows developers. While UWP apps have their roots in the XAML apps of Windows 8, some key differences give developers some major advantages when building apps for the platform.

A key advantage is the universal aspect of these apps. Microsoft builds versions of Windows 10 to run on different device families, listed as follows:

• Desktop (PC)
...

XAML is based on Extensible Markup Language (XML). This would seem like a great thing as XML is a flexible markup language familiar to most developers. It is indeed flexible and powerful, but it has some drawbacks.

The primary problem with Microsoft’s implementations of XAML is that there have been so many variations of the XAML language created for different development platforms over the years. Currently, WinUI/UWP, Windows Presentation Foundation (WPF), and .NET MAUI (formerly Xamarin.Forms) applications all use XAML as their UI markup language, in addition to some third-party UI frameworks. However, each of these uses a different XAML implementation or schema, and the markup cannot be shared across the platforms. In the past, Windows 8, Silverlight, and Windows Phone apps also had additional.

If you have never worked with XAML before, you’re probably ready to see an example of some UI markup. The following XAML is a fragment that defines Grid containing...

The WinUI library is a set of controls and UI components that has been extracted from the Windows SDK and included in the Windows App SDK. After this separation, many controls have been enhanced and others have been added. The Windows App SDK is being developed in the open. Its issues are tracked on GitHub and with input from Microsoft and the Windows developer community.

So, if these WinUI libraries are based on UWP libraries in the Windows SDK, you may be wondering why you should choose WinUI as your UI framework instead of UWP. UWP has been around since the launch of Windows 10 and is quite robust and stable. There are several very good reasons to consider WinUI.

Choosing WinUI brings with it many of the benefits of open source software (OSS). OSS is typically very reliable. When software is developed in the open by an active developer community, issues are found and resolved quickly. In fact, if you find an issue with an open source package, you can fix it...

Unlike WinUI 2.0 and the incremental versions that followed, WinUI 3 is a major update featuring more than new and improved controls and libraries to use with Windows desktop apps. In fact, the primary goal of WinUI 3 was not to add new controls and features beyond its current UWP counterparts. The Windows App SDK team has made WinUI a complete UI framework that can sit atop the Windows desktop .NET platform.

Goodbye UWP?

So, what is happening to UWP? Will our UWP apps stop working?

As previously mentioned, the plan for the UWP UI libraries is to keep providing important security updates, but they will not receive any new features going forward. It is likely that WinUI 2.8 will be the final 2.x version. All new features and updates will be developed for WinUI and the Windows App SDK. New applications will be developed in WinUI with either .NET, written in C# or VB, or with native C++. These clients will sit on top of the Win32 platform. This is...

Where does WinUI fit into the overall landscape of Microsoft’s Windows development frameworks? Let’s draw some comparisons to help answer that question, starting with those that are most like WinUI.

WinUI versus UWP

This is a tricky comparison because WinUI apps today share the same XAML schema as UWP apps. In fact, WinUI 2.x are controls for UWP applications. They share the same XAML schema, base visuals, and underlying Windows APIs. Any UWP app that has the same minimum and target versions of Windows specified can add the WinUI 2.x libraries to leverage the new and updated features. However, UWP will not receive any feature updates beyond WinUI 2.8. Only security and bug-fix updates will be released as 2.8x minor releases.

A key difference between apps that use WinUI versus traditional UWP apps is access to new and updated controls and other visual elements without requiring an updated Windows SDK. This...

We covered a lot of the history of Windows application development in this chapter. We learned about the origins of UWP and its roots in Windows 8 apps and learned of the benefits of XAML when building Windows UIs. We had a taste of what some simple WinUI app code and UIs look like. Finally, we examined the recent history of WinUI versions and how WinUI 3 is a complete replacement for the UWP UI libraries and a viable option for WPF developers going forward.

This will give you a good foundation of what’s to come as we start building an app with WinUI in the chapters ahead. In the next chapter, you will set up your development environment, learn about the app project that we will create throughout the book, and create your first WinUI 3 project. When we get to Chapter 3, MVVM for Maintainability and Testability, we will refactor the app to use the MVVM pattern. This will set us up with a solid, maintainable design as we later add to and extend the app throughout the...

1. Which version of Windows first introduced UWP apps to developers?
2. What is the name of the pattern commonly used by WinUI and other XAML developers to separate the UI logic from the business logic?
3. WinUI and WPF apps can share the same XAML. True or false?
4. Which was the first Microsoft UI framework to use XAML to define the UI?
5. What was the version number of the first WinUI release?
6. What is one of the benefits of developing with WinUI over WinForms?
7. Can WinUI apps only be developed with .NET languages?
8. Challenge: create a style that will apply to Button elements.