We are supporting a major Belgian utilities organisation on a range of business-critical digital and system modernisation initiatives. For a long-term programme, we are looking for a strong .NET Fullstack Developer with proven WPF expertise to help evolve and maintain operator-facing and internal platforms. This role requires someone who is genuinely comfortable building rich desktop applications in WPF, alongside solid backend development in .NET. Logistics Role: Freelance .NET Fullstack Developer (WPF Focus) Contract: 12–24 months Location: Brussels (Hybrid – 2 days/week on-site) Languages: English French or Dutch Start Date: ASAP / Flexible Rate: Competitive & negotiable Responsibilities Design, develop, and maintain applications using .NET / C# Build and enhance rich desktop solutions using WPF (Windows Presentation Foundation) Contribute to both new development and modernisation of existing systems Translate complex business and operational requirements into scalable technical solutions Develop and maintain backend services and APIs Ensure clean architecture, code quality, and maintainability Participate in Agile ceremonies, code reviews, and technical discussions Collaborate with cross-functional teams to deliver reliable, high-performance solutions Required Skills 5 years of experience as a .NET Developer Strong expertise in C# and the .NET ecosystem Proven, hands-on experience with WPF (essential) Experience building fullstack solutions (desktop frontend backend services) Solid knowledge of REST APIs and relational databases Experience with Git-based workflows and CI/CD environments Comfortable working autonomously within Agile/Scrum teams Experience on large, business-critical systems Nice to Have Experience in the utilities or energy sector Exposure to legacy system modernisation projects Knowledge of Azure or cloud environments Familiarity with enterprise-scale architecture and performance considerations If you’re a strong .NET developer with deep WPF experience looking for a long-term freelance engagement within a high-impact utilities' environment, we’d be happy to discuss further.