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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: 40644204
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34 freelancers are bidding on average $2,039 USD for this job

Hi — Elias here from Miami. I see you’re looking to enhance your team with full-stack developers skilled in ASP.NET, Legacy .NET, and React. It’s clear that your goal is to build robust applications that meet evolving business needs. What usually matters most here is ensuring the architecture is scalable and maintainable. A common issue in systems like this is managing legacy code while integrating modern frameworks. The tricky part is usually balancing performance with the complexity of user roles and workflows. My approach focuses on creating a solid foundation that prioritizes stability and future-proofing. I typically structure systems to allow for seamless updates and easy integration of new features. This minimizes disruption and enhances user experience. I've worked on various platforms where I managed similar challenges, ensuring smooth transitions between legacy and modern systems. A few questions to better understand the scope: Q1 – What specific user roles and permissions are you envisioning for the application? Q2 – How do you plan to handle integrations with existing systems? Q3 – What are your scaling expectations as user demand grows? Happy to go through the details and suggest the best technical approach. Looking forward to hearing from you.
$2,500 USD in 10 days
6.9
6.9

Hi, I reviewed your need for a full-stack developer to maintain legacy .NET Framework systems, extend ASP.NET Core APIs, and deliver React-based UI improvements. I’ll bridge old and new by enhancing Web Forms/MVC/WCF apps, building well-tested ASP.NET Core services and REST APIs, and implementing responsive React features with clean component architecture and reliable state management. I focus on maintainable software architecture, strong production troubleshooting, and clear internal documentation, while collaborating smoothly with product and design. Let’s discuss here now.
$1,500 USD in 30 days
5.5
5.5

Hi there, we have recently completed a similar project and would love to share some references. I see you're looking to maintain and modernize legacy .NET applications while enhancing your platform with ASP.NET Core and React. We excel at bridging old and new technologies, ensuring critical systems run smoothly while guiding their evolution. Our focus is on delivering clean, maintainable code that saves you time and minimizes errors. Here's how we'd approach it: - Assess and refactor legacy code for better performance. - Develop responsive front-end features in React. - Collaborate closely with your team to ensure alignment on features. - Implement best practices for documentation and code reviews. While we might be newer to Freelancer, we bring 9+ years of experience delivering this kind of work off-platform and multiple 5-star reviews to back it up. Feel free to reach out for a free consultation on your project, even if you don’t hire us. Kind regards, Trichelle
$1,800 USD in 7 days
5.4
5.4

⭐⭐⭐⭐⭐ Full-Stack Developer for ASP.NET & React to Modernize Your Software ❇️ Hi My Friend, I hope you're doing well. I've reviewed your project requirements and I see you are looking for a Full-Stack Developer. Look no further; Zohaib is here to help you! My team has successfully completed 50+ similar projects for Full-Stack Development. I will maintain and modernize your software platform by working on both legacy .NET applications and ASP.NET Core services. I can also build and enhance user-facing features in React, ensuring everything runs smoothly. ➡️ Why Me? I can easily handle your project as I have over 5 years of experience in C# and .NET development, including legacy systems. My skills cover ASP.NET Core, React UI development, and database management. Additionally, I have a strong grip on REST APIs and Git workflows, allowing me to deliver high-quality work efficiently. ➡️ Let's have a quick chat to discuss your project details. I would love to show you samples of my previous work. Looking forward to our chat! ➡️ Skills & Experience: ✅ C# ✅ ASP.NET Core ✅ Legacy .NET Framework ✅ React ✅ SQL Server ✅ REST APIs ✅ Git ✅ MVC ✅ Web Forms ✅ WCF ✅ Problem-Solving ✅ Code Reviews Waiting for your response! Best Regards, Zohaib
$1,800 USD in 2 days
4.6
4.6

Hi, Aashiq (Ash) here from Cape Town, South Africa. This project instantly caught my eye, so I had to reach out. I see you’re looking for a Full-Stack Developer who can bridge legacy .NET applications with modern ASP.NET and React. That’s right up my alley, as I’ve spent over five years honing my skills in C# and .NET, while also diving deep into React for front-end development. I’ve helped several businesses modernize their software platforms, ensuring smooth transitions while maintaining critical functionalities. If you’d like, I can share samples of my successful projects that demonstrate my expertise. Based on what you mentioned, here is how we would approach the project: - Assess existing legacy applications for modernization opportunities - Develop APIs and services using ASP.NET Core - Create responsive front-end features in React - Collaborate closely with your team for seamless feature delivery You can count on clear communication and a user-focused solution optimized for performance throughout our collaboration. Best Regards, Aashiq
$2,700 USD in 7 days
3.8
3.8

Hi there! I noticed you're working with legacy .NET Framework apps alongside modern ASP.NET Core—are you looking to gradually migrate everything over, or do you need both systems running in parallel for the foreseeable future? Regardless, this is definitely something that I feel confident delivering on, given my past experience. I would love to discuss your project further! Looking forward hearing from you. kind regards, Corné
$1,800 USD in 7 days
3.6
3.6

With over 7 years of experience in C#/.NET development, I specialize in maintaining and modernizing software platforms, specifically bridging the gap between legacy .NET applications and modern technologies like ASP.NET Core and React. My expertise includes refactoring legacy codebases, migrating systems to newer frameworks, and improving overall architecture. Skilled in ASP.NET Core, React, and SQL Server, I excel in designing, building, and maintaining services, APIs, and user-facing features. Experience with Git, CI/CD pipelines, and collaborative workflows ensures smooth teamwork and adherence to best practices. Eager to explore integrations with Azure or AWS, leverage TypeScript, and implement microservices architecture for improved scalability and performance. I am keen on understanding your roadmap for future scalability, security considerations, and modernization timelines to align our objectives for mutual success and potential growth within the organization. Let's connect to discuss how I can contribute to your project's success through innovation and collaboration.
$2,700 USD in 5 days
3.0
3.0

Hi, Your role is a strong fit for someone who can move comfortably between legacy .NET Framework, ASP.NET Core, and React. I understand the main need is keeping existing systems stable while steadily modernizing them without slowing delivery. I’ve worked on C# and .NET applications that needed both maintenance and incremental upgrades, including API work, frontend features, and cleanup of older code. I’m comfortable tracing issues across the stack, refactoring carefully, and writing maintainable code that fits into an existing team workflow. My approach would be to first understand the current architecture, identify the highest-risk areas, and then deliver improvements in small, safe steps. I focus on clear code, practical testing, and communication that keeps everyone aligned. If you’d like, I’m ready to discuss how I can help move this platform forward. Best regards, Gabriel
$1,500 USD in 20 days
2.4
2.4

Hi, This role fits the kind of engineering work I value: understanding the existing system before changing it, keeping business-critical applications stable, and modernizing them in controlled, testable increments. I’d begin by mapping the legacy .NET applications, dependencies, database contracts, deployment process, and production risks. For modernization, I prefer extracting clear service boundaries and adding characterization tests before replacing working code. This makes it possible to move Web Forms, MVC, or WCF functionality toward ASP.NET Core without creating an unplanned rewrite. On the modern side, I’m comfortable structuring ASP.NET Core APIs with clear contracts, validation, authentication, logging, and reliable error handling. In React, I focus on typed, reusable components, predictable state, responsive layouts, and avoiding unnecessary renders. I’d also contribute through concise PRs, code reviews, SQL analysis, production troubleshooting, documentation, and CI/CD improvements. I’m comfortable working remotely and independently while keeping technical decisions visible to the wider team. The stated monthly range is understood, subject to clarifying hours, responsibilities, and contract terms. Regards, Houssame
$2,250 USD in 7 days
3.9
3.9

Seattle, United States
Member since Aug 6, 2026
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