Senior Full Stack .NET Engineer (Legacy Windows App)

Hi there :) Thanks for checking in to find out about our open position. We´ll provide as much information as possible, but please feel free to reach us if you have further questions. We´ll be happy to see your application, even if there are skills you don't quite master! ABOUT US We partner with high-growth companies to bring elite software engineers from Latin America who are not just technically strong but also AI-fluent and built for long-term partnerships. Our engineers integrate seamlessly into your team, working in your tools, your timezone, and with the same level of ownership your in-house team brings. ABOUT THE CLIENT Our client is a global nonprofit dedicated to family history and genealogy, helping millions of people around the world discover and preserve their family stories. Engineering for them means supporting the systems that power large-scale digitization of historical archives collected from repositories worldwide. ABOUT THE ROLE You will maintain and modernize a Windows desktop application used by field teams to capture and organize digitized historical records. This includes fixing user-reported defects, resolving nightly and automated build failures, and supporting new version releases. You will work across both modern and legacy portions of the codebase, and partner with the security team to bring the application in line with organizational security standards. This is a full-time role requiring full overlap with Mountain Time working hours. WHAT YOU NEED TO SUCCEED - Strong C#/.NET experience (.NET 8.0), including advanced C# features and nullable reference types. - WPF (XAML, data binding, styles, custom controls) and MVVM architecture (CommunityToolkit.Mvvm). - Entity Framework 6 (database-first development, LINQ, DbContext, migrations). - SQL Server (T-SQL, LocalDB, database design, query and performance optimization). - Dependency Injection with Autofac and interface-driven application design. - Visual Studio / MSBuild (project configuratio