Senior C# Developer — Excel Add-in

We’re hiring an experienced C#/.NET engineer to build a production-grade Excel add-in that streamlines complex workflows and improves analyst productivity. You’ll own the add-in end to end—from architecture and UI to deployment and support.

What you’ll do
• Partner with stakeholders to turn business requirements into a clear technical plan and release roadmap.
• Design and develop a Windows Excel add-in (Ribbon, task panes, context menus) ---------- with Office interop (e.g., VSTO, Add-in Express, or Excel-DNA).
• Implement features such as custom functions, automation flows, data transformation tools, and intuitive UX inside Excel.
• Integrate with external APIs/services; handle auth, rate limits, and error handling gracefully.
• Optimize for performance and stability (event handling, cross-threading, COM release, large workbooks).
• Create installer(s) and deployment artifacts (MSI/Setup), code signing, and versioning suitable for enterprise rollout.
• Build tests, add logging/telemetry, and write concise user/administrator documentation.
• Provide maintenance, triage, and iterative improvements post-launch.

Must-have qualifications
• 4+ years professional experience with C#/.NET building desktop applications or Office add-ins.
• Hands-on experience with Excel add-in development on Windows via VSTO, Add-in Express, or Excel-DNA (not VBA-only).
• Strong knowledge of Excel object model, COM interop, and memory management (e.g., Marshal.ReleaseComObject, event lifecycles).
• UI development with WinForms or WPF (custom task panes, dialogs, forms).
• Solid software engineering practices: SOLID, async patterns, exception handling, automated builds, and Git.
• Ability to translate business problems into robust, maintainable solutions.

Nice to have
• Experience packaging/distributing add-ins at scale (MSI/Setup.exe), code signing certificates, and update strategies.
• Familiarity with ---------- libraries for data and HTTP (e.g., JSON serialization, REST clients, SQLite/embedded storage).
• Performance profiling for large workbooks; background processing and responsive UIs.
• Secure credential storage, configuration management, and role-based features.
• (Bonus) Office.js experience and an understanding of differences vs. COM add-ins.

Platform note: This project targets Microsoft Excel for Windows (Microsoft 365 / Office 2019+; 64-bit preferred). Cross-platform (Mac/Excel Online) is a plus but not required for this role.

What you’ll deliver
• A reliable, signed Windows Excel add-in with installer(s).
• Feature set agreed in the spec (custom functions/tools/UI).
• Unit/integration tests and basic telemetry/logging.
• Admin and end-user documentation, plus a short support handoff.

How to apply

Please send:
• Your resume and a short cover letter explaining relevant add-in experience.
• Links to portfolio/GitHub or code samples (ideally an Excel add-in you’ve built).
• Two–three sentences on how you’d structure the solution (tooling, interop approach, deployment).
• And tell us your favorite color so we know you read the posting.

We value clear communication, craftsmanship, and pragmatic problem-solving. If that’s you, we’d love to hear from you.