Freelance or permanent

Tasks and responsibilities

In a public-sector digital-services environment, you will develop secure, accessible and responsive business applications that support citizens, healthcare professionals and internal users in Belgium. You will work across the application stack, from the Blazor user interface to the .NET services behind it, while contributing to technical decisions and supporting colleagues.

You will join an ICT department of approximately 250 professionals working on more than 50 projects in different development phases. The organisation is modernising its application landscape towards a cloud-native architecture on Microsoft Azure, using Azure Service Bus and containerised workloads. A platform engineering team provides shared libraries, the design system, DevOps pipelines and standards for the application teams.

Web user interfaces are standardised on Blazor, allowing one .NET skill set to cover the complete application. The UI is the part of the application used by citizens, healthcare professionals and employees, so it must be accessible, consistent and responsive. The organisation is also exploring the responsible use of AI in business applications and software development.

Job purpose

As Senior .NET Developer with a UI focus, you will design, develop, integrate and maintain modern business applications. You will take ownership of their user interfaces while contributing to the underlying services. The role combines advanced hands‑on development with technical leadership, coaching and close collaboration with analysts, architects, UX stakeholders, security specialists, the platform engineering team and operations.

You will translate functional and technical requirements into reusable, accessible solutions. Your work will support a consistent user experience across devices and browsers, correct integration with services and APIs, reuse of the shared component library and design system, and compliance with standards for architecture, security, quality, maintainability and delivery.

As a senior developer, you will help resolve complex technical issues, make well‑founded design choices, improve engineering practices and support colleagues through coaching and code reviews. The role remains strongly hands‑on, with direct contributions to feature development, testing, troubleshooting and continuous improvement across both the UI and its supporting services.

Key responsibilities

• Provide technical direction for Blazor development across teams and promote consistent UI architecture, reusable components, coding standards and engineering practices in line with the platform team's standards.
• Develop features, reusable components, prototypes, technical improvements and bug fixes using C#, modern .NET, Blazor, Razor components and the .NET Web APIs on which they depend.
• Design scalable, maintainable and reusable front‑end structures that align with the organisation's architectural principles, and contribute to the shared component library built on MudBlazor and the shared design system.
• Build responsive interfaces with semantic HTML and modern CSS that meet WCAG 2.1 level AA, as required of Belgian public bodies under the European Web Accessibility Directive. Consider usability, browser compatibility and the public‑service context throughout the development process.
• Work with functional and business analysts and UX stakeholders to clarify requirements, assess feasibility and translate user and business needs into sound technical solutions.
• Integrate Blazor applications with REST APIs and JSON‑based services, including typed clients, suitable error handling, state management, validation and resilience. Extend the Web APIs when a feature requires it.
• Implement secure authentication and authorisation flows using OAuth 2.0 and OpenID Connect for internal users, healthcare professionals and citizens, each with its own identity provider. Apply secure development practices throughout the application lifecycle.
• Maintain code quality through structured pull‑request reviews, refactoring, SonarQube static analysis, coding standards and clear, reusable and testable components.
• Define and maintain unit tests, Blazor component tests with bUnit, service‑level integration tests and, where appropriate, automated UI tests with Playwright. Follow the test pyramid to support reliable releases and prevent regressions.
• Use Git, Azure DevOps repositories, boards and CI/CD pipelines for controlled versioning, automated builds, testing and deployment to Azure environments.
• Select the appropriate Blazor render mode for each application, monitor and improve loading time, rendering behaviour and responsiveness, and use Dynatrace and browser tools to diagnose issues in test and pro