Avalonia in pure C#

[WhispererX]

I'm making my own programming language and I'm at the point where everything is functional and I want to add a module to build graphical applications. Of course Avalonia is practically the only choice, given that it is cross-platform. There's zero documentation on using it in pure C# instead of XAML though.

It is an interpreted language so all I want is to wrap avalonia tools to my programming language functions. That includes building multiple windows, styling, etc.

I did try to do something with chat gpt (again, there's no documentation elsewhere), the created window always ended up being transparent and I could not give it a solid colored background no matter what.

So I'm not asking for full documentation of course, could anyone just help me set it up, have the window appear with a solid background at least lol.

[robloo]

Avalonia didn't originally have XAML support and was completely C#. All that functionality is still there and fully supported. A number of projects leverage it. i.e. https://github.com/AvaloniaUI/Avalonia.Markup.Declarative

Don't forget that XAML itself is compiled to C# as well.

Documentation for this probably should be expanded over time.

[stevemonaco]

Small clarification. XAML in Avalonia consumes CLR types and emits IL.

[robloo]

Whoops. I knew that too... thanks for the correction!

[timunie]

Check out repros from @wieslawsoltes . He has several samples, for example https://github.com/wieslawsoltes/NXUI

[WhispererX]

Thanks, very useful material.

[stevemonaco]

@stevensrmiller created some samples, more based around rendering than UI, over at https://github.com/stevensrmiller/AvaloniaWithoutXAML

I generally discourage the practice for many reasons. The only uncontested benefit, IMO, is that you stay entirely within standard .NET tooling. You will still need to learn XAML eventually because all themes (Avalonia's and third-party) have been written using XAML and you need to read the ControlThemes to have full understanding of how to customize them. It's not a shortcut.

[WhispererX]

Thanks for the link, I'll check it out. I'll look into theming aswell.

[thevortexcloud]

See also this old discussion: #9006

Anyway: I don't know much about how the XAML compiler works, but I imagine you can use that with your language, assuming the language is interpreted at runtime by .NET? You can certainly load XAML at runtime already.

If you are using a non ,NET language you can technically get it to work as well by using AOT. It's a bit cursed though. See this library which exposes Avalonia to Rust:

https://github.com/sourcegear/bridge-info/tree/main/samples/rust/Avalonia

The accompanying blog posts also explain how it works:

https://ericsink.com/native_aot/index.html

[WhispererX]

I'll check out the links. FYI my language is interpreted directly in C#

[thevortexcloud]

In that case: You should be able to use the runtime XAML loader.

Avalonia/src/Markup/Avalonia.Markup.Xaml.Loader/AvaloniaRuntimeXamlLoader.cs

Lines 15 to 25 in 5483217

	/// <summary>
	/// Loads XAML from a string.
	/// </summary>
	/// <param name="xaml">The string containing the XAML.</param>
	/// <param name="localAssembly">Default assembly for clr-namespace:.</param>
	/// <param name="rootInstance">The optional instance into which the XAML should be loaded.</param>
	/// <param name="uri">The URI of the XAML being loaded.</param>
	/// <param name="designMode">Indicates whether the XAML is being loaded in design mode.</param>
	/// <returns>The loaded object.</returns>
	[RequiresUnreferencedCode(XamlX.TrimmingMessages.DynamicXamlReference)]
	public static object Load([StringSyntax(StringSyntaxAttribute.Xml)] string xaml, Assembly? localAssembly = null, object? rootInstance = null, Uri? uri = null, bool designMode = false)

Avalonia will build a .NET object from it which you can do whatever you want with.