Senior Desktop UI Engineer (C# / WinUI 3)

7+ years of experience

Ukraine

Remote

For our client, we are looking for a Senior Desktop UI Engineer (C# / WinUI 3) for a 6-month engagement with the possibility of extension. The core purpose of this role is to serve as the technical authority and principal developer for our application's user interface. You will drive all major architectural decisions for the frontend, establish best practices, and implement the most critical and complex UI features. Your mission is to build a scalable, performant, and maintainable UI architecture that not only meets today's needs but is also robust enough to support future innovation.

Responsibilities:

Architect and lead the end-to-end development of the application's frontend using WinUI3, XAML, and C#.
Own the technical strategy for the UI layer, making critical decisions on component libraries, state management, and architectural patterns.
Design and implement highly complex, interactive UI components, including custom-built data visualizations, high-performance virtualized data grids, and sophisticated custom controls.
Engineer a robust and intuitive multi-window and multi-monitor experience.
Implement robust client-side logic to communicate with backend services, consuming both high-performance gRPC streams and standard RESTful APIs.
Integrate and optimize real-time video streaming components within the WinUI 3 framework.
Champion and enforce the MVVM (Model-View-ViewModel) design pattern, dependency injection, and other best practices to ensure a decoupled and scalable codebase.
Rigorously profile, diagnose, and resolve performance bottlenecks related to UI rendering, data binding, and memory consumption.
Collaborate with product and backend teams to define and refine technical requirements, ensuring frontend capabilities align perfectly with backend services.
Partner with QA and DevOps to define and implement a comprehensive UI test automation strategy, ensuring the application is architected for testability.
Mentor other engineers (as the team grows) and establish the gold standard for code quality, testing, and development processes for the frontend.

Qualifications:

7+ years of professional software engineering experience, with a recent focus on frontend/UI development.
Proven, hands-on professional experience building and shipping applications with WinUI 3 and the Windows App SDK.
Expert-level proficiency in C# and an in-depth understanding of the .NET ecosystem (.NET 6/7/8).
Experience building clients that consume backend services using both REST APIs and gRPC.
Mastery of a XAML-based technology (WPF, UWP), with a recent and primary focus on WinUI 3.
Expert-level knowledge and practical application of software architecture and design patterns, especially MVVM, Dependency Injection (DI), and Repository patterns.
Demonstrable experience architecting solutions for complex UI challenges, such as handling large datasets, virtualization, and multi-threading in the UI.
Deep experience with asynchronous programming (async/await) and its practical application in creating responsive user interfaces.
A bachelor's degree in Computer Science, Engineering, or a related field, or equivalent professional experience.

Preferred Skills:

Experience developing custom controls from the ground up in WinUI/XAML.
Familiarity with advanced performance and memory profiling tools for .NET (e.g., PerfView, dotTrace, dotMemory).
Experience with UI automation frameworks for Windows applications (e.g., WinAppDriver, Appium, Playwright).
Knowledge of video streaming protocols (e.g., RTSP, WebRTC) and their integration challenges within a native desktop client.
Experience setting up and maintaining CI/CD pipelines for Windows applications using MSIX packaging (e.g., Azure DevOps, GitHub Actions).
A strong portfolio or GitHub profile showcasing advanced desktop application development projects.