Karl W.

I'm a senior .NET developer with over 12 years on Upwork, specialising in Windows desktop applications, legacy system work, and business integrations across the Microsoft stack. My background is broad, but where I'm most useful is on the harder projects — undocumented codebases, legacy migrations, ERP integrations, and end-to-end delivery of complex Windows software. These are the kinds of projects I've built a reputation around. A recent example: I designed and built a full Windows Assistant platform using WPF — combining video capture, SharePoint content management with a Windows Explorer-style interface, a locally cached SQLite database with a background sync service, and a Web API built on a clean services/infrastructure architecture over Entity Framework Core and SQL Server. The system included SignalR real-time notifications, JWT authentication, and integrations with Vimeo, Twilio, SmileBack and others, alongside a complete MVC admin portal. What I work on: Legacy systems — VB6, Visual FoxPro, VB.NET, WinForms, WPF. I regularly take on codebases other developers decline, and I'm comfortable working in undocumented or inherited code. ERP and business integrations — SAP, SAGE, MYOB, SQL Server, Oracle, Shopify, DocuSign, Amazon API and more. I've worked across insurance, logistics, and enterprise clients and understand how business-critical systems need to behave. I ask the right questions before I start, flag issues early, and deliver on time. Clients tend to come back for that as much as the technical work. Tech I work with: WPF · WinForms · C# · .NET / ASP.NET · WCF · Entity Framework Core · SQL Server · Oracle · SQLite · SignalR · JWT · REST APIs · SharePoint · MS Office Add-ins · SAP · SAGE · MYOB · VB6 · VB.NET · Visual FoxPro · Shopify · DocuSign · Amazon API · Vimeo · Twilio · MVC