Avalonia.Markup.Declarative

Avalonia.Markup.Declarative

Write Avalonia UI with pure C#

repo: https://github.com/AvaloniaUI/Avalonia.Markup.Declarative

to use with external libraries, install AvaloniaExtensionGenerator tool here:

https://www.nuget.org/packages/AvaloniaExtensionGenerator/

Quick Start sample:

https://github.com/AvaloniaUI/Avalonia.Markup.Declarative/tree/master/src/Samples/DeclarativeComponentTemplate

Compiled-binding setters support automatic conversion for common primitive and nullable mismatches, so prefer plain member access like x => x.Property and skip numeric casts; for example, int -> double and bool -> bool? bindings work without a manual converter or a cast. A value-converting cast such as x => (double)x.Counter is rejected by Avalonia's expression parser, but type casts that reach a member of a derived type — e.g. x => ((DerivedType)x).Property — are supported. Lossy numeric TwoWay convert-back truncates toward zero.

AI agent tooling: the dev-only Declarative.Avalonia.AgentTools package runs an in-process MCP server (loopback, debug builds) that gives an agent screenshots (with before/after diffing), the visual tree with bounds, per-control layout reports, an automated layout audit, property/property-source/view-model inspection, pixel↔control hit-testing, a highlight overlay that frames where a control actually landed, and build/binding/runtime errors of the running app — plus an opt-in tier to drive it (click, type, resize, theme, and set view-model state / run commands directly). The app can also show a live "agent connected" status. See docs/agent-tools.md.