Available for freelance work

Modernising Legacy Apps
into Maintainable
Web & Cross-Platform.

I help companies modernise legacy desktop applications into maintainable web and cross-platform components — without losing the business logic that took years to build. Full-stack .NET developer with 4 years of experience. Fluent in German and English. Remote-ready.

4 yrs experience German C1 English C1
Get in touch
Stefan Simić

Tech Stack

React TypeScript C# / .NET ASP.NET Core Web API .NET MAUI Blazor Hybrid SQL Server PostgreSQL Git Postman Visual Studio Rider

Experience

Where I've worked

Freelance Full-Stack Developer
Self-employed
2025 – present
  • Contributed to modernisation of legacy WinForms applications into maintainable, cross-platform components using .NET MAUI and Blazor Hybrid for mid-sized DACH companies.
  • Developed cross-platform applications with ASP.NET Core Web APIs and SQL Server.
  • Provided technical consulting and implementation support across multiple industries.
Full-Stack Developer
ADVANT Beiten – Munich, Germany
Apr 2023 – Aug 2025
  • Migrated a legacy ERP system (WinForms) to React and .NET Core Web API; designed the MSSQL database schema and built REST APIs.
  • Maintained and extended the existing WinForms system with regular updates, bug fixes and new features.
Software Developer
Agenda Informationssysteme – Rosenheim, Germany
Mar 2022 – Mar 2023
  • Maintained and extended a payroll accounting system in Delphi; contributed to internal tools using C# and .NET Core.
  • Analysed and resolved system errors, implemented new features and ensured system stability.

Projects

Selected Work

Transport App Demo
Full-Stack + Mobile

Transport App

Full-stack transport platform (ASP.NET Core + React) extended to mobile via .NET MAUI and Blazor Hybrid. Supports offline usage, cross-platform deployment (iOS/Android/Windows) and a shared web/mobile component architecture.

ASP.NET Core React .NET MAUI Blazor Hybrid iOS / Android / Windows
Rent a Car Demo
Desktop & Web

Rent a Car

Vehicle rental management system with customer and vehicle management, reservations, billing and reporting. Built as both a C# desktop app and a web application.

C# ASP.NET Core SQL Server Windows Forms

Let's work together.

Have a project in mind? I'd love to hear about it.

stefan@stefansimic.dev