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Full-Stack Developer — ASP.NET, Legacy .NET & React Remote | Full-Time About the Role We're looking for a versatile Full-Stack Developer to help us maintain, modernize, and extend our software platform. You'll work across a mix of legacy .NET Framework applications and modern ASP.NET Core services, while building and improving user-facing features in React. This is a great fit for someone who's comfortable bridging old and new — keeping critical systems running while helping guide their evolution. What You'll Do Maintain and enhance existing applications built on legacy .NET Framework (Web Forms, MVC, or WCF) Design, build, and maintain services and APIs using ASP.NET Core Develop responsive, maintainable front-end features using React Participate in modernization efforts — refactoring legacy code, migrating to .NET Core/5+, and improving overall architecture Write clean, well-tested, maintainable code and participate in code reviews Collaborate with product managers, designers, and other engineers to scope and deliver features Troubleshoot and resolve production issues across the stack Contribute to technical documentation and internal best practices What We're Looking For 5+ years of professional experience with C# / .NET, including exposure to legacy .NET Framework applications Solid experience with ASP.NET Core (Web API, MVC, or Razor Pages) Hands-on experience building UI with React (hooks, component architecture, state management) Working knowledge of SQL Server or another relational database Comfort working with REST APIs and understanding of software design patterns Experience with Git and collaborative development workflows Strong problem-solving skills and the ability to work independently across unfamiliar codebases Nice to Have Experience with Azure or AWS Familiarity with CI/CD pipelines Exposure to TypeScript Experience modernizing or migrating legacy systems Understanding of microservices or service-oriented architecture Salary range: $1500 - $2000 / month
Project ID: 40653708
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52 freelancers are bidding on average $1,931 USD for this job

Hi, I’m Elias, a Miami-based senior software engineer with 20 years of experience in full-stack development, including ASP.NET, Legacy .NET, and React. I’ve reviewed your project and understand that you're seeking skilled developers to enhance your team and deliver high-quality software solutions. I have built similar systems that emphasize secure architecture, responsive UI, and scalability. My approach would involve: 1) Understanding your specific business workflows and technical requirements. 2) Designing a user-friendly experience and robust architecture. 3) Developing core features and necessary integrations. 4) Conducting thorough testing to ensure everything functions smoothly. 5) Deploying the solution and providing ongoing support post-launch. Could you please clarify the following questions to help me better understand the project? 1) What legacy systems will the new development need to integrate with? 2) Are there specific user roles or permissions we should consider? 3) What edge cases or unique business logic should we be aware of? I’ve successfully completed similar projects, most under NDA, so while I can’t share specific links, I’d be happy to discuss the architecture and features I implemented. Additionally, I can ensure a maintainable codebase, making future updates easier for your team.
$2,000 USD in 10 days
6.9
6.9

Hello!, I am a Florida-based senior software engineer(frontend, backend, ecommerce, etc) with 15+ years of experience in ASP.NET, legacy .NET, and React. I read your project carefully. You’re not just looking for a developer, but someone who can work comfortably in older .NET code, handle full-stack delivery, and keep the UI and implementation quality solid. My approach: 1. Review the current codebase and workflow 2. Identify risks, quick wins, and priority areas 3. Implement changes cleanly with testing 4. Keep communication clear and consistent I’ve worked on SaaS platforms, internal tools, and modern React frontends, and I’m very comfortable stepping into existing systems where stability and maintainability matter. I care about doing the job properly, not just getting it done fast. Could you please clarify the following questions to help me better understand the project? 1. What parts of the ASP.NET / legacy .NET codebase need the most immediate attention? 2. Is the React frontend already built, or would this role include frontend development and refactoring too? 3. What would you consider a successful first milestone for this role? If helpful, I can also share relevant examples of similar work I’ve done in SaaS dashboards, legacy modernization, and React-based portals. If you want someone who pays attention to details and can own the work seriously, I’d be glad to connect. -James
$2,300 USD in 8 days
6.5
6.5

I can support your full-stack modernization plan spanning legacy .NET Framework and modern ASP.NET Core services, while strengthening React UI features. I’m comfortable bridging old and new codebases, stabilizing critical Web Forms/MVC/WCF components, then incrementally refactoring toward cleaner architecture and maintainable APIs. Execution focuses on: production-safe enhancements and bugfixes across the stack; ASP.NET Core Web API/MVC/Razor Pages services with RESTful design patterns; React development with hooks, component architecture, and state management; SQL Server-backed data work and performant queries; Git-based collaborative workflows; and disciplined, testable code with reviews. I’ll help reduce migration risk by addressing refactors in small, verifiable steps (including .NET Core/5+ migration paths), improving documentation and internal best practices so your team can scale delivery confidently.
$1,500 USD in 5 days
5.4
5.4

✋ Hi There!!! ✋ THE PROJECT GOAL: MAINTAIN, MODERNIZE AND EXTEND LEGACY .NET SYSTEMS WITH ASP.NET CORE AND REACT. 1. Maintain and enhance legacy .NET Framework applications including Web Forms, MVC and WCF. 2. Develop reliable ASP.NET Core APIs and modern backend services. 3. Build responsive React features using hooks, components and state management. 4. Refactor legacy code, support migrations and improve overall architecture. 5. Troubleshoot production issues while following Git, testing and documentation practices. Similar full-stack projects have been completed across C#, .NET Framework, ASP.NET Core, React, REST APIs and SQL-based systems. <-- Questions --> 1. Which legacy .NET applications should be prioritized for modernization? 2. Is Azure or AWS currently used for deployment and infrastructure? Looking forward to chat with you for make a deal Best Regards Elisha Mariam!
$1,500 USD in 7 days
4.9
4.9

Hello, I appreciate the opportunity to apply for the Full-Stack Developer position. I understand that you need someone who can maintain and modernize your software platform while integrating legacy .NET applications with modern ASP.NET Core services and React features. With over 5 years of professional experience in C# and .NET, I have successfully worked on various projects involving legacy .NET Framework applications, as well as developing responsive UI components using React. My expertise in ASP.NET Core, combined with a solid understanding of REST APIs and SQL Server, positions me well to contribute effectively to your team. To achieve your project goals, I would take the following approach: - Assess and optimize existing legacy applications, ensuring critical systems remain operational while planning for modernization. - Design and implement new services and APIs using ASP.NET Core, enhancing functionality and performance. - Develop and refine front-end features in React, ensuring a seamless user experience. - Collaborate closely with product managers and engineers to deliver features on time and meet project requirements. I am eager to begin this project and confident in my ability to deliver high-quality results. I am available to discuss further details at your convenience. Thank you for considering my proposal.
$1,500 USD in 7 days
4.3
4.3

Hi, Aashiq (Ash) here from Cape Town, South Africa. This project instantly caught my eye, so I had to reach out. I see you are looking for a Full-Stack Developer to maintain and modernize your software platform, specifically bridging legacy .NET applications with modern ASP.NET Core and React. With over five years of experience in C# and .NET, I have successfully helped companies enhance their systems, ensuring smooth transitions while improving user experiences with cutting-edge technologies. I can share examples of how I’ve contributed to similar projects that achieved impressive results. Based on what you mentioned, here is how we would approach the project: - Assess and refactor legacy applications for better performance - Build new features in ASP.NET Core and React - Collaborate closely with your team to ensure alignment with project goals - Troubleshoot and optimize existing systems I assure you of clear communication and a seamless, user-focused solution optimized for performance. Best Regards, Aashiq
$2,700 USD in 7 days
4.5
4.5

GIVE ME 30 SECONDS TO SHOW YOU WHY I'M THE RIGHT FIT FOR THIS PROJECT. I successfully modernized a legacy .NET application for a client, migrating it to ASP.NET Core and implementing a React front-end. This project increased performance by 40% and improved user satisfaction, showcasing my ability to bridge old and new technologies. I have over 6 years of experience in C# and .NET, with a strong focus on legacy systems and modern frameworks. My hands-on work with ASP.NET Core and React makes me well-equipped for enhancing your software platform. I understand your goal of maintaining critical systems while guiding their evolution. I will ensure a smooth transition by refactoring legacy code and implementing best practices. My commitment to clear communication and effective execution will contribute to long-term success in your projects. I am excited to help you achieve exceptional results. The difference between an average result and an exceptional one is usually decided before the work even begins. Regards Patrick
$1,500 USD in 7 days
4.1
4.1

Hi, This role makes sense—balancing legacy systems with modern stacks while keeping things running is a common challenge. The mix of Web Forms, ASP.NET Core, and React suggests you need someone who can navigate old and new code without making things worse. I’ve worked on projects where ASP.NET MVC apps were gradually migrated to Core while React frontends replaced aging UI layers. Usually the tricky part isn’t the shiny new parts—it’s making sure the legacy integrations don’t break when changing things like WCF endpoints or SQL Server dependencies. For the React work, I’d start by mapping the data flow from the ASP.NET Core APIs into the frontend, making sure the state management fits the actual usage patterns. The React parts will need to be modular enough to avoid a complete rewrite later. One thing that often trips people up is the database layer. If the legacy code is tightly coupled to specific SQL Server features, touching it without breaking reports or background jobs can get messy. We’d handle that by isolating changes behind clean interfaces. I can start working right away. Let's connect and discuss the details. Thanks, Denis.
$1,500 USD in 20 days
3.6
3.6

Hi there, I work across C#, .NET Framework, ASP.NET Core, React, REST APIs, and SQL-based systems, with a strong focus on maintaining existing applications while modernizing them carefully without disrupting production. From your scope, I see the role as a mix of legacy support and forward development: keeping Web Forms/MVC/WCF applications stable, building new ASP.NET Core services, improving React features, and gradually moving older parts of the platform toward a cleaner and more maintainable architecture. I’m comfortable working inside unfamiliar codebases, debugging production issues, following Git-based workflows, and collaborating with product and engineering teams. I’m also available for a full-time engagement and can align with your team’s working hours. A few things I’d like to clarify: Which .NET Framework and ASP.NET Core versions are currently in production? Are there specific legacy modules already prioritized for migration or refactoring? Is the React frontend mainly JavaScript today, or are you already using TypeScript? I would love to discuss the platform and current priorities further. Feel free to share a suitable time for a quick call or chat. Regards, Muhammad Taqi (FK)
$2,250 USD in 7 days
3.4
3.4

Hello, "FULL-STACK .NET AND REACT DEVELOPMENT" — you need someone who can keep legacy systems stable while moving features forward. I’d approach this by first understanding the existing .NET architecture, then improving it step by step with ASP.NET Core APIs and React features without disrupting current users. The key challenge is modernizing older code safely while keeping business-critical workflows running. Which part needs the most attention first: legacy .NET modernization, new React features, or backend API improvements? Looking forward to working with you. — Truong
$1,500 USD in 1 day
3.1
3.1

Hello, With over five years of professional experience in C#/.NET, I have worked extensively with both legacy .NET Framework applications and modernized equivalents, including ASP.NET Core. My solid background in maintaining and enhancing existing applications includes Web Forms, MVC, or WCF - the exact skills required for your project. Furthermore, I have hands-on experience building UI using React for user-facing features just like the ones you're seeking to build and improve.
$1,500 USD in 2 days
2.8
2.8

Hi, this role clearly needs someone who can work comfortably across legacy .NET Framework, ASP.NET Core, and React while keeping production systems stable. I’ve handled full-stack work in similar environments where older Web Forms or MVC code had to be maintained alongside newer APIs and UI features. My approach is to first understand the existing architecture, identify the safest changes, and then improve the codebase in small, testable steps. I focus on clean C# code, solid API design, and React components that are easy to maintain. I’m also careful with refactoring and troubleshooting, especially when working in unfamiliar codebases. If you’d like, I can help keep the platform running smoothly while moving it forward. Best regards, Gabriel
$1,500 USD in 20 days
2.4
2.4

I've maintained and modernized legacy .NET Framework apps while building new ASP.NET Core services and React frontends—so this stack is familiar ground. I'll start by auditing the existing Web Forms/MVC and WCF services, then set up a parallel ASP.NET Core environment for gradual migration. For the frontend, I'll structure React components with hooks and state management matching your current setup, ensuring seamless integration with the legacy APIs via REST adaptation layers. I'll enforce Git workflows for code reviews and set up CI pipelines on Azure DevOps for automated testing and deployment. I can start immediately. Thanks, Andrii
$2,250 USD in 30 days
2.3
2.3

Hello, the biggest challenge here isn’t just the mix of legacy .NET Framework and modern ASP.NET Core — it’s keeping the old Web Forms or WCF parts running smoothly while gradually replacing them without breaking anything in production. Recently I worked on a migration project where we had to maintain a large WCF backend while slowly rolling out ASP.NET Core microservices for new features. The trick was isolating legacy endpoints behind adapters and writing tests that ran against both stacks. On the frontend, we rebuilt a React app to consume both old SOAP endpoints and new REST APIs using a facade layer. For this role I’d start by mapping the legacy surface area, then set up parallel environments for gradual migration. I’d keep the React part decoupled with TypeScript and state management that works with both old and new backends. Azure DevOps pipelines would handle CI/CD for both stacks. I’d need access to the current codebase and a brief on which parts are slated for immediate modernization. Also, what’s the current deployment process for the legacy apps? Thanks, Lazar.
$1,500 USD in 30 days
1.8
1.8

Hi, 10+ years across .NET + React, with the ability to maintain legacy systems while moving them toward a cleaner modern architecture — that’s exactly the kind of work I can take ownership of. What I can bring to your team: ✓ C# / .NET Framework / ASP.NET Core ✓ Web API, MVC, REST APIs & SQL ✓ React, component architecture & state management ✓ Legacy code maintenance, debugging & refactoring ✓ Gradual .NET Core/5+ modernization ✓ Git-based collaborative development and production support I’m comfortable entering an unfamiliar existing codebase, identifying dependencies before making changes, and delivering improvements without disrupting critical functionality. Availability: Full-time / Long-term Rate: Within your $1,500–$2,000 monthly range I’m ready for a technical interview or coding assessment and can start immediately. Regards, Ravi B.
$2,000 USD in 30 days
2.0
2.0

Hi There!!! i understand you are looking for a full time full stack developer who can maintain legacy .NET Framework applications, build and extend services in ASP.NET Core, and develop responsive front-end features in React, while also contributing to modernisation and migration efforts across the stack. My services would cover maintaining and enhancing existing legacy applications, designing and building APIs in ASP.NET Core, developing UI features in React with proper state management, refactoring older code toward modern architecture, working with SQL Server for data needs, and collaborating closely with your product and engineering team on ongoing delivery. Let's have a quick chat so we can go through the current codebase and modernisation priorities together. Best Regards, Hussain Ahmed
$1,500 USD in 26 days
1.5
1.5

Hello!! Your platform needs a dependable full-stack developer who can maintain legacy .NET applications, build ASP.NET Core services, and develop modern React features while gradually improving the overall architecture. • Is the current platform mainly Web Forms, MVC, or WCF? • Which part of the system needs attention first? • Are Azure or AWS environments already configured? The development approach will focus on safe modernization without disrupting critical existing systems. Clean C# code, reliable REST APIs, responsive React interfaces, database work, testing, Git workflows, production troubleshooting, and gradual migration can all be handled within one development process. Relevant full-stack and legacy modernization projects have been completed, connecting proven systems with modern technology while keeping reliability at the center. Let us discuss your current codebase and long-term development needs. Best regards Farhin B
$1,515 USD in 7 days
2.9
2.9

I can develop your full-stack .NET and React platform, modernizing legacy .NET applications, building ASP.NET Core APIs, React features, SQL integrations, and CI/CD workflows. Ready to start immediately.
$1,500 USD in 7 days
0.0
0.0

Based in Lahore, Pakistan, and comfortable working full-time across legacy and modern .NET stacks. The main challenge here is modernizing incrementally without destabilizing business-critical Web Forms/MVC/WCF code, so I’d first map dependencies and test coverage before moving modules toward ASP.NET Core. My work covers C#, .NET, REST APIs, SQL-backed systems, React/TypeScript, Git workflows, debugging, and production issue resolution. I’m comfortable entering unfamiliar codebases, fixing legacy behavior first, then refactoring where it actually reduces risk. For modernization work I’d prefer small migration slices with regression tests and CI checks rather than a large rewrite.
$1,500 USD in 7 days
0.0
0.0

As a veteran software developer with over 5 years of professional experience and exposure to both modern and legacy .NET frameworks, I am uniquely equipped for your project's needs. Not only am I comfortable navigating and enhancing existing applications built on Web Forms, MVC or WCF, but I also boast solid skills in ASP.NET Core, including Web API, MVC and Razor Pages. What's more, my experience extends to designing, building and maintaining services and APIs using ASP.NET Core and developing responsive front-end features with React. I'm confident my past projects altering extensions and themes for various platforms like WordPress, Magento and Shopify demonstrates my proficiency in code refactoring and migration – providing me relevant expertise in improving your architecture. Additionally, my robust problem-solving skills have allowed me to work independently across unfamiliar codebases in the past. Integrating my skill set with your prospective projects would offer me exciting new challenges while ensuring efficient operation within the team. Lastly, aside from practical experience with SQL Server, REST APIs, Version control Systems (e.g., Git), cloud service providers (e.g., Azure/AWS) etc., my refined working knowledge of C#, .NET Frameworks and other relevant tools signifies that I hit the ground running offering no tedious learning curve; allowing immediate value addition to your project. I hope we get to work together soon. Thank you for considering me!
$2,250 USD in 7 days
0.0
0.0

Seattle, United States
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