10/16/2026 updated
MS
100 % available
Senior C# / .NET Backend Developer | Legacy Modernisation, REST APIs, Blazor, Avalonia
Warsaw, Poland
Only remote
• Higher National Diploma, Electronics and Electrical Engineering, Fife College, Kirkcaldy, ScotlandAbout me
Senior C#/.NET backend contractor, 20+ years B2B. I modernise legacy .NET Framework systems (WCF, Oracle, NHibernate) to .NET 8+ and build REST APIs, Blazor and Avalonia apps. Clients: Rolls-Royce, AXA, Tauron. 100% remote from Poland, in English, flexible hours incl. US time zones.
GitHub ActionsAzure DevOpsASP.NET.NET FrameworkMicrosoft AzureC Sharp (Programming Language)LinuxEntity FrameworkGitHubInternet Information Services (IIS)Windows Communication FoundationJSONMicrosoft Visual StudioMicrosoft SQL ServersNHibernate
C# and .NET Backend Development
Over 20 years of commercial experience in C# backend development, covering both legacy .NET Framework codebases and modern .NET 10 applications. Expertise in ASP.NET, ASP.NET Core, REST APIs, WCF services, microservices, and IIS.
Database and ORM Expertise
Extensive work with MS SQL Server and Oracle databases, combined with deep knowledge of Entity Framework, NHibernate, and custom ORM implementations in large enterprise systems.
Cloud and DevOps with Microsoft Azure
Hands-on experience with Microsoft Azure, Azure DevOps, VSTS, Git, Docker, and Linux for deploying, testing, and maintaining applications in cloud environments.
Blazor and Frontend Development
Practical experience building web frontends with Blazor Server, MudBlazor, ASP.NET Web Pages, and Three.js for 3D rendering in the browser.
Avalonia UI Desktop Development
Development of cross-platform desktop applications using Avalonia UI, including automation tooling integrated with existing enterprise products.
Legacy Application Modernisation
Specialisation in modernising large legacy .NET Framework applications, migrating features to current .NET versions while maintaining business continuity.
E-Commerce System Development
End-to-end development of e-commerce platforms from scratch, including 3D product configurators, customer management, checkout systems, and admin interfaces.
Requirements Gathering and Solo Delivery
Direct collaboration with clients and end users to gather requirements, combined with the ability to deliver complete projects independently from start to finish.
C++ Basics
Basic knowledge of C++ as a supplementary language alongside primary C# and .NET development work.
Over 20 years of commercial experience in C# backend development, covering both legacy .NET Framework codebases and modern .NET 10 applications. Expertise in ASP.NET, ASP.NET Core, REST APIs, WCF services, microservices, and IIS.
Database and ORM Expertise
Extensive work with MS SQL Server and Oracle databases, combined with deep knowledge of Entity Framework, NHibernate, and custom ORM implementations in large enterprise systems.
Cloud and DevOps with Microsoft Azure
Hands-on experience with Microsoft Azure, Azure DevOps, VSTS, Git, Docker, and Linux for deploying, testing, and maintaining applications in cloud environments.
Blazor and Frontend Development
Practical experience building web frontends with Blazor Server, MudBlazor, ASP.NET Web Pages, and Three.js for 3D rendering in the browser.
Avalonia UI Desktop Development
Development of cross-platform desktop applications using Avalonia UI, including automation tooling integrated with existing enterprise products.
Legacy Application Modernisation
Specialisation in modernising large legacy .NET Framework applications, migrating features to current .NET versions while maintaining business continuity.
E-Commerce System Development
End-to-end development of e-commerce platforms from scratch, including 3D product configurators, customer management, checkout systems, and admin interfaces.
Requirements Gathering and Solo Delivery
Direct collaboration with clients and end users to gather requirements, combined with the ability to deliver complete projects independently from start to finish.
C++ Basics
Basic knowledge of C++ as a supplementary language alongside primary C# and .NET development work.
Experience
Professional experience10+ years
Freelancer since2004
Languages
EnglishFluentPolishNative speaker
Project history
Maintaining a .NET Framework (ASP.NET Web Pages) application for one of Poland's largest energy groups, and moving its features to a new .NET 8 application with an in-house front-end framework. Tech: C#, .NET Framework, .NET 8, ASP.NET Web Pages, Oracle, NHibernate, WCF, IIS.
Built the whole shop for a skydiving jumpsuit manufacturer from scratch: a 3D configurator, customer measurements, checkout and admin. Gathered requirements directly with the owner in weekly and daily calls. Tech: C#, .NET 10, Blazor Server, MudBlazor, Three.js, MS SQL, Entity Framework, Docker, Linux.
Extended the company's main product, a legacy .NET Framework codebase with a custom ORM and a custom DSL. Built a desktop tool in Avalonia UI that automates work on the main product. Built task management software in Blazor, integrated with Azure DevOps. Tech: C#, .NET Framework, .NET, Blazor, Avalonia UI, Azure DevOps.