Senior Developer .NET

Mission Overview:

As a Senior .NET Developer, you will play a key role in designing, developing, and maintaining robust software solutions based on Microsoft technologies. You will bring your technical expertise to ensure code quality, solution sustainability, and system performance. Additionally, you will serve as a technical mentor for other team members. This position is a consultancy mission at a client site representing Keystone Solutions.

Responsibilities:

• Actively participate in the development of software components in .NET (Framework and Core);
• Design scalable technical solutions in collaboration with the architecture team;
• Provide technical coaching to team members and foster a culture of excellence;
• Conduct code reviews and ensure adherence to best development practices;
• Analyze functional requirements with analysts and translate them into technical solutions;
• Ensure the quality, performance, security, and maintainability of applications;
• Participate in optimizing system performance;
• Integrate and evaluate new technologies in line with business objectives.

Behavioral Skills:

• Critical analysis and information integration skills;
• Structured and solution-oriented thinking;
• Ability to generate viable alternatives and draw relevant conclusions;
• Technical leadership and collaborative spirit;
• Resilience and adaptability to technical or contextual changes.

Language Skills:

• Fluency in one of the two national languages: FR or NL (level C2);
• Very good level of English (level C1).

We offer an interesting job in ICT and Data services that impacts society, with numerous advantages:

• A good work-life balance;
• Flexible working hours within a 40-hour week (7:30 AM to 8:00 PM with fixed slots between 9:00 AM and 12:00 PM and 1:00 PM and 4:00 PM);
• Possibility of remote work;
• Workspaces organized according to activities;
• Easy accessibility via public transport;
• Car and bike parking in the building;
• Individual lockers;
• Company restaurant;
• Various self-development opportunities: training and learning possibilities (to be pursued outside working hours) via our e-academy self-training platform or through the Microsoft Enterprise Skills Initiative platform.

If you are ready to tackle technical and strategic challenges in a dynamic consultancy environment, apply today at Keystone Solutions Career Portal .

Duration: 14/09/2026 - 31/12/2026 4 months • (full time)

Skills required:

• ASP .NET Web API - Level: Confirmed - Most recent: Any time
• Authentication/Authorization (JWT, OIDC, claims) - Level: Confirmed - Most recent: Any time
• Blazor - Level: Junior - Most recent: Any time
• C# / .NET (Core, 10) - Level: Confirmed - Most recent: Any time
• Entity Framework Core - Level: Confirmed - Most recent: Any time
• MVC - Level: Confirmed - Most recent: Any time
• REST API's - Level: Confirmed - Most recent: Any time
• REST, Swagger/OpenAPI - Level: Confirmed - Most recent: Any time
• SQL Server - Level: Confirmed - Most recent: Any time
• Testing (unit + integration) - Level: Confirmed - Most recent: Any time

Language requirements:

Dutch
Level Active knowledge
English
Level Active knowledge
French
Level Active knowledge