Middle/Senior .NET UI Developer (Avalonia/WPF, WebAssembly)

About the project
We are building a new industrial web platform designed to run both as an Azure-hosted SaaS solution and as an air-gapped on-premises installation from a shared codebase.
The platform uses modern .NET technologies, with Avalonia UI powering the user interface across browser-based WebAssembly and desktop applications.
You will help build the core UI framework, creating a reusable, modular, and high-performance interface for industrial dashboards and data-intensive applications.
The stack is .NET 10, ASP.NET Core, PostgreSQL/TimescaleDB, Keycloak, Docker and Kubernetes, with all UI in Avalonia.

We are looking for a Middle/Senior Frontend Developer with strong C#/.NET and Avalonia UI experience to build the user interface of a new industrial web platform running in the browser through WebAssembly and sharing code with desktop applications.

This is a UI-focused engineering role, not a traditional JavaScript frontend position. We are looking for someone experienced in building complex interfaces, reusable components, and UI architecture using Avalonia, or strong WPF/XAML expertise combined with hands-on Avalonia experience.

Requirements
5+ years of commercial experience with C# and .NET, including modern .NET versions.
Production experience with Avalonia UI, or strong WPF/XAML experience combined with hands-on Avalonia development.
Solid understanding of MVVM, dependency injection, and asynchronous programming.
Experience building custom controls, styles, themes, and data-intensive interfaces such as grids, charts, and dashboards.
Ability to write maintainable, testable code and collaborate through Git-based code review workflows.
Availability to work remotely from within the EU and overlap with the US East Coast working hours from 08:00 to 13:00 ET.

Nice to have
Experience migrating desktop applications from WPF or WinForms to Avalonia.
Hands-on experience with Avalonia UI running in the browser through WebAssembly and understanding of its limitations.
Familiarity with LiveCharts2, ScottPlot, OxyPlot, or commercial UI control libraries.
Experience with plug-in systems or modular UI architectures.
Unit testing of view models and automated testing practices.
Knowledge of OIDC authentication, Keycloak, notifications, and file uploads.
Experience optimizing WebAssembly applications through trimming, AOT compilation, or lazy loading.
Familiarity with accessibility standards (WCAG) and localization.
Experience building industrial, IIoT, manufacturing, or other data-intensive dashboard applications.
Basic knowledge of ASP.NET Core and REST/OpenAPI.

Responsibilities

• Build the Avalonia UI shell: navigation, layouts, user preferences, and responsive and touch-friendly design.
• Create a reusable component library and themes (light, dark, high-contrast), with customer branding kept separate from themes.
• Implement UI extension points so plug-ins can add pages, dashboards and settings, with visibility driven by roles and licenses.
• Test and help select charting and control libraries for Avalonia WASM.
• Set up the localization architecture and port existing WPF screens to Avalonia.
• Optimize WASM load time and performance across the four target browsers.
• Write unit tests, take part in code reviews, and document UI decisions.