WinUI 3: A Practical Deep Dive

Table of contents

Introduction

Right, let’s talk about WinUI 3. If you’ve been building Windows desktop applications for any length of time, you’ve probably noticed the UI framework landscape has been… complicated. We’ve had WinForms, WPF, UWP, and now WinUI 3. Each promising to be “the future” of Windows development.

I’ve spent considerable time with WinUI 3 over the past year, and I want to share an honest assessment. Not the marketing version – the actual, practical reality of building applications with this framework.

Prerequisites

Before diving in, this post assumes you’re familiar with:

• XAML-based UI development (WPF or UWP experience helps)
• .NET development fundamentals
• Visual Studio 2022 or later

What Actually is WinUI 3?

Here’s the short version: WinUI 3 is Microsoft’s latest UI framework, shipped as part of the Windows App SDK. It’s essentially the UWP XAML visual layer, but decoupled from UWP’s restrictive deployment model.

The practical benefit? You get modern, native Windows UI components without the UWP baggage. You can target Windows 10 1809 onwards, use traditional deployment methods, and access Win32 APIs directly when needed.

Performance: The Good News

I’ll be honest – I was sceptical about the performance claims initially. Microsoft’s marketing tends toward optimism. But the numbers have genuinely impressed me.

Startup Times

WinUI 3 applications start noticeably faster than UWP equivalents. The main reason? No .NET Native compilation overhead. UWP’s ahead-of-time compilation was meant to improve runtime performance, but it killed startup times. WinUI 3 with standard .NET JIT compilation feels snappier.

Memory Footprint

The framework uses less memory than WPF for comparable applications. In my testing with a moderately complex LOB application, I saw roughly 15-20% lower working set compared to the WPF equivalent. Native rendering and a more efficient visual tree contribute to this.

Building Custom Controls

One area where WinUI 3 genuinely shines is custom control development. The templating system is mature (inherited from years of XAML evolution), and the patterns are consistent.

Here’s a practical example – a custom button with an additional text property:

public sealed class CustomButton : Control
{
    public CustomButton()
    {
        this.DefaultStyleKey = typeof(CustomButton);
    }

    public static readonly DependencyProperty ButtonTextProperty = 
        DependencyProperty.Register(
            nameof(ButtonText), 
            typeof(string), 
            typeof(CustomButton), 
            new PropertyMetadata(string.Empty));

    public string ButtonText
    {
        get => (string)GetValue(ButtonTextProperty);
        set => SetValue(ButtonTextProperty, value);
    }
}

If you’ve done this in WPF, you’ll feel right at home. The API is nearly identical, which means your existing XAML skills transfer directly.

C++/WinRT Interop

For teams with mixed C# and C++ codebases, WinUI 3 offers genuine interoperability. The same control in C++/WinRT:

struct CustomButton : winrt::Microsoft::UI::Xaml::Controls::ControlT<CustomButton>
{
    winrt::hstring ButtonText();
    void ButtonText(winrt::hstring const& value);
    static winrt::Microsoft::UI::Xaml::DependencyProperty ButtonTextProperty();
};

Different syntax, same underlying APIs. This matters for performance-critical components or when wrapping existing native libraries.

The Honest Challenges

Now for the less comfortable bits. WinUI 3 isn’t without problems, and you should know about them before committing to a project.

Backward Compatibility Constraints

Windows 10 1809 is the floor. That might sound reasonable, but I’ve encountered enterprise clients still running 1709 or earlier. If your user base includes slower-moving IT departments, this constraint needs early discussion.

Ecosystem Gaps

The third-party control ecosystem is thin compared to WPF. Telerik, DevExpress, and others are adding WinUI 3 support, but the catalogue isn’t as comprehensive. You may find yourself building controls that would be off-the-shelf in WPF.

Documentation Quality

Microsoft’s docs are improving, but there are gaps. You’ll occasionally find yourself piecing together solutions from GitHub issues, Stack Overflow, and the WinUI source code itself. Budget extra time for research on less common scenarios.

Tooling Rough Edges

The XAML designer in Visual Studio still has reliability issues. Hot reload works, but not as consistently as in WPF. These friction points add up during daily development.

Trade-offs and Considerations

When to Choose WinUI 3

Based on my experience, WinUI 3 makes sense when:

• You’re targeting Windows 10 1809+ exclusively
• Modern, native Windows appearance matters
• You need tight Windows 11 integration (snap layouts, mica, etc.)
• Your team has existing XAML experience
• You’re starting a new project rather than migrating

Stick with WPF when:

• You need Windows 7/8 support
• Your project relies heavily on third-party controls
• You’re maintaining an existing WPF application
• Time-to-market is critical and your team knows WPF well

Conclusion

WinUI 3 represents genuine progress for Windows desktop development. The performance is real, the modern controls look genuinely good, and the decoupling from Windows releases means faster iteration.

But it’s not yet a complete replacement for WPF in all scenarios. The ecosystem needs time to mature, the tooling needs polish, and the documentation needs filling out.

My recommendation? For new projects targeting modern Windows with a team willing to navigate some rough edges, WinUI 3 is increasingly the right choice. Just go in with realistic expectations rather than marketing-fuelled optimism.