Senior .NET Developer

Senior .NET Developer – Brussels (Hybrid). For a major organization operating in the Belgian public sector / healthcare & social security industry, we are looking for an experienced Senior .NET Developer to join a team developing and maintaining business-critical applications.

Location: Brussels – Hybrid.

Onsite: Minimum 2 days/week.

Start: 14/09/2026.

Initial duration: Until 31/12/2026 – Full-time.

The Role: As a Senior .NET Developer, you will play a key role in designing, developing and maintaining robust applications based on Microsoft technologies. You will combine hands-on development with technical leadership, ensuring high standards regarding code quality, security, performance and maintainability.

Key Responsibilities: Develop software components using C# / .NET Framework and .NET Core; Design scalable and maintainable technical solutions in collaboration with architects; Develop and integrate REST APIs / Web APIs; Translate functional requirements into technical solutions; Perform code reviews and promote development best practices; Mentor and provide technical guidance to other developers; Ensure application quality, security, performance and maintainability; Optimize application and system performance; Evaluate and integrate new technologies when relevant.

Technical Skills: Strong experience with: C# / .NET Core / modern .NET; ASP.NET Web API; REST APIs; Swagger / OpenAPI; Entity Framework Core; SQL Server; MVC; Authentication & Authorization – JWT, OIDC, Claims; Unit & Integration Testing. Experience with Blazor is considered an advantage.