Senior .NET Developer

Senior .NET Developer (Freelance) - 4 Months - Borgerhout (Antwerp) Belgium

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About the Role

We are seeking a Senior .NET Developer (Freelance) for a 4-month project with our client in Borgerhout (Antwerp), Belgium. This is a high-impact opportunity to architect, develop, and optimize mission-critical applications within a modern Microsoft technology stack. You’ll be at the heart of a team that’s shaping digital transformation in a complex, real-world environment.

Why This Role Matters

As a Senior .NET Developer, you will drive the creation of robust, scalable, and maintainable software solutions that directly impact operational excellence and patient care in a hospital context. Your expertise will empower our client to deliver seamless integrations, elevate user experiences, and ensure the reliability of essential systems. The stakes are high — your work will help solve real business challenges and set new standards for quality and innovation.

Key Responsibilities

• Lead the analysis, design, development, testing, documentation, and support of .NET-based applications and data integrations.


• Coach and mentor fellow developers, fostering a culture of technical excellence and continuous improvement.


• Collaborate closely with architects, infrastructure specialists, analysts, application managers, and other developers to deliver end-to-end solutions.


• Write, analyze, and optimize SQL queries for high-performance data access.


• Develop and maintain RESTful APIs, ensuring secure and efficient data exchange.


• Implement modern component-based UI solutions using HTML5, CSS3, and JavaScript.


• Apply Agile methodologies, taking a proactive role in sprint planning, reviews, and retrospectives.


• Ensure code quality, maintainability, and scalability through best practices in software architecture and design patterns.


• Contribute to CI/CD pipelines and advocate for automation and continuous delivery principles.


• Support and enhance authentication and authorization mechanisms (OAuth2, OpenID Connect, JWT).


• Model data, design indexes, views, and stored procedures to optimize database performance.

Technical Skills

• Senior-level experience in .NET development (C#, ASP.NET).


• Proven track record in developing .NET-based applications.


• Expertise in writing, analyzing, and optimizing SQL queries.


• Hands-on experience with relational databases, especially Microsoft SQL Server.


• Strong background in developing RESTful APIs and understanding API design principles, HTTP methods, status codes, and JSON exchange.


• Solid knowledge of HTML5, CSS3, and JavaScript for modern UI development.


• Familiarity with authentication and authorization mechanisms such as OAuth2, OpenID Connect, or JWT.


• Understanding of data modeling, indexes, views, and stored procedures.


• Knowledge of software architecture and design patterns.


• Experience with CI/CD principles and tools.

Language Proficiency

• Fluency in Dutch at European CEFR level C2 is required.

Other Requirements

• Demonstrable experience in leading a development team and coaching developers.


• Proven ability to execute programming tasks efficiently: coding, testing, and debugging.


• Experience working in a hospital or healthcare context is highly valued.


• Demonstrable education with certification or equivalent experience in relevant programming languages and environments.


• Strong knowledge and hands-on experience with Agile development methodologies, with the ability to take on a leading role.