Add the Rich Text Editor package to your project

dotnet add package Avalonia.Controls.RichTextEditor

Include your Avalonia UI license key in the executable project file .csproj

<ItemGroup>
    <AvaloniaUILicenseKey Include="YOUR_LICENSE_KEY" />
</ItemGroup>

Add a RichTextEditor in your XAML view

<RichTextEditor>
    <RichTextEditor.Document>
        <FlowDocument>
            <Paragraph>
                <RichRun Text="Welcome to " />
                <RichBold>
                    <RichRun Text="RichTextEditor" />
                </RichBold>
                <RichRun Text="!" />
            </Paragraph>
        </FlowDocument>
    </RichTextEditor.Document>
</RichTextEditor>

Or create programmatically in C#

var document = new FlowDocument();
var paragraph = new Paragraph();
paragraph.Inlines.Add(new RichRun("Hello "));
paragraph.Inlines.Add(new RichBold(new RichRun("World")));
paragraph.Inlines.Add(new RichRun("!"));
document.Blocks.Add(paragraph);

editor.Document = document;

No. This component is part of the Avalonia Pro and Enterprise tiers. Activation requires an Avalonia account and a valid Pro or Enterprise licence.

Yes. Each component gives you a ready UI out of the box, but you can build a bespoke interface by using the underlying classes directly and wiring up your own commands and visuals.

Supported formats depend on the underlying platform. Check the component's documentation and the platform's own capability lists for specifics.

Avalonia UI components support Windows, macOS, Linux, iOS, Android, and WebAssembly. Each component uses the native platform back-end for optimal performance and compatibility.