Senior C#/.NET Engineer (Desktop, SQL, ERP Integration)

Gensoft is looking for a Senior C#/.NET Engineer for a contract engagement with an international manufacturing company. The goal is to replace a business-critical Excel/VBA tool for spare parts booking with a reliable, maintainable desktop application integrated with the company's stock and ERP processes.
The client expects hands-on experience with AI coding tools, combined with strong engineering judgement and careful testing and verification of everything that ships.

About the project
Three operational workflows currently run on a set of Excel/VBA workbooks: spare parts booking, stock counting and label generation. Spare parts booking is the first priority.
The new application will:
read stock data through an agreed Microsoft Dynamics NAV integration;
write booking transactions to a dedicated SQL table as soon as an operator books stock out;
pass data to ERP through the client's existing posting mechanism;
support enterprise single sign-on;
work with the existing 2D barcode scanners (compatibility to be confirmed).
The .NET version, desktop framework and integration details are still open and will be agreed during discovery. The other two workflows will be assessed afterwards to decide whether to fix, keep or replace them.

What you'll do
Analyse the existing workbooks, formulas and VBA code and uncover the business rules behind them
Clarify and validate requirements with the client's applications team and operational users
Identify defects and outdated workarounds that shouldn't move into the new solution
Agree a prioritised backlog and realistic delivery increments
Design and build the C# application using an approved AI-assisted workflow, owning code review, technical decisions and testing
Implement stock retrieval, transactional writes, SSO and barcode scanner support
Define permissions, transaction history and safeguards
Support QA and UAT, deliver deployment instructions and maintenance documentation
Raise dependencies, risks and scope constraints early

Requirements
Strong commercial experience with C#/.NET, including delivery of maintainable desktop applications
Solid SQL skills, including reliable transactional writes
Experience integrating with ERP or similar transactional business systems
Ability to read and understand Excel formulas and VBA
Enterprise SSO integration experience
Practical experience configuring and directing AI coding tools or agents, and the ability to explain how you review and verify generated code
Good understanding of data validation, concurrency, failed transactions and duplicate submissions
Ability to make pragmatic architectural decisions when requirements are incomplete
Clear technical English and confident communication with stakeholders
Comfortable owning delivery with minimal day-to-day direction

Nice to have
Microsoft Dynamics NAV
Barcode scanner integration, especially 2D scanners
Inventory, warehouse or manufacturing systems
Replacing Excel/VBA tools with proper business applications
Taking software through QA, UAT and operational handover
No specific industry experience is required.

Engagement details
Contract, full-time, fully remote
Initial term: 4 months, extension possible
Start: ASAP
Good overlap with UK business hours, especially during discovery
AI tooling: GitHub Copilot (licence provided by the client); other tools only with client approval
Local development on a client-provided test database, following the client's security and data handling rules