
Closed
Posted
Paid on delivery
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: 40648126
51 proposals
Remote project
Active 4 days ago
Set your budget and timeframe
Get paid for your work
Outline your proposal
It's free to sign up and bid on jobs
51 freelancers are bidding on average $1,826 USD for this job

Greetings! I can work as a Full-Stack Developer on your platform, maintaining legacy .NET Framework applications, building ASP.NET Core services, and developing React front-end features. I have experience with C#, SQL Server, REST APIs, and Git. I am comfortable bridging old and new codebases. Let me know your preferred start date and I will begin. Thanks, Revival
$1,500 USD in 30 days
8.0
8.0

In the rapidly evolving world of software development where versatility is key, I am the perfect match for your project as a Full-Stack Developer. With over five years of solid experience working with C#/.NET, including exposure to legacy .NET Framework applications and a knack for modernizing and improving them, I will help extend your existing software platform while keeping critical systems running smoothly. On top of that, I bring hands-on expertise building UI with React, along with proficiency in ASP.NET Core (Web API, MVC, or Razor Pages). Your project's need to bridge old and new is highly familiar to me as I strive to design, build and maintain services and APIs that are evergreen yet responsive. And it's not just about code: my collaborative nature allows me to work seamlessly with product managers, designers, and fellow engineers - a true team player. Aside from technical skills, I offer clear daily communication and progress updates, clean well-documented code, on-time delivery and publishing support, long-term maintenance and technical assistance. You can expect full dedication from me towards modernizing your platforms while maintaining smooth running. Let's transform your platform together!
$2,250 USD in 7 days
4.7
4.7

✋ Hi There!!! ✋ THE PROJECT GOAL: MODERNIZE AND EXTEND LEGACY .NET SYSTEMS WITH REACT 1. 9+ years experience with C# and .NET, including legacy Web Forms, MVC and WCF. 2. Strong ASP.NET Core experience building REST APIs and maintainable services. 3. React development with hooks, components and state management for responsive UI. 4. Skilled with SQL databases, Git, testing, code reviews and production troubleshooting. 5. Experienced in legacy modernization, .NET migration, cloud deployment and scalable architecture. Similar projects include modernizing legacy .NET applications, developing ASP.NET Core APIs and building React dashboards with clean architecture. <-- Questions --> 1. Which legacy applications should be prioritized for modernization? 2. Is the current platform hosted on Azure, AWS, or on-premise? Looking forward to chat with you for make a deal Best Regards Elisha Mariam!
$1,511 USD in 11 days
4.9
4.9

Greetings, Your project stood out because it needs someone who can handle both sides of the stack without treating the legacy system as something to simply replace. I can work across C# and .NET Framework applications, ASP.NET Core APIs, SQL databases, and React, while gradually improving the existing architecture without putting working business features at risk. I can take care of legacy Web Forms, MVC or WCF code, build and extend modern REST services, develop clean React components, troubleshoot production issues, and handle modernization or migration work where it makes sense. I am also comfortable with Git based workflows, code reviews, testing, documentation, and working independently inside an unfamiliar codebase. My focus would be keeping the current platform stable while making each part easier to maintain and extend. I would be happy to first understand your existing architecture and identify where I can bring the most value. PS: I would rather let the quality of my work convince you than make big promises here. Give me a small part of the system to review and I believe the difference will be clear. If you found my proposal satisfactory it would be delighted for me to talk more about your project in detail. Best Regards, Shawana Y
$2,250 USD in 7 days
3.9
3.9

Hi, I have strong experience with C#/.NET, ASP.NET Core, React, REST APIs, SQL, and modernizing existing applications. I’m comfortable working across both legacy .NET Framework codebases and modern services, troubleshooting production issues, and delivering clean, maintainable features. I can handle API development, React UI, database work, legacy refactoring, .NET migrations, Git workflows, testing, and architecture improvements. I’m also comfortable joining an existing team, understanding unfamiliar codebases quickly, and working independently on ongoing development and modernization. I’m available for long-term remote work and can contribute from day one across both frontend and backend. I’d be happy to discuss your current platform, priorities, and development workflow.
$1,800 USD in 7 days
4.5
4.5

Hi there! Quick question - are you planning to keep both the legacy .NET Framework and ASP.NET Core systems running in parallel during modernization, or will you be gradually phasing out the old stack? 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

Hello! As a highly skilled and experienced Full-Stack Developer, I believe I have the necessary expertise to help maintain, modernize, and elevate your software platform. With over 5 years of experience working with C#/.NET, substantial knowledge of ASP.NET Core and proficiency in working with React, I can comfortably leverage these skills to bridge the gap between your pre-existing legacy framework and your goal to migrate to newer technologies. Throughout my career, I have consistently demonstrated my ability to write clean, well-tested code. My eye for detail coupled with strong problem-solving skills would allow me to navigate unfamiliar codebases seamlessly and troubleshoot and resolve production issues proficiently - a crucial requirement for this project. Additionally, having worked with REST APIs extensively and my familiarity with SQL Server makes me well-suited to deliver the desired features integrating these key components. Moreover, you can be assured of my dedication, efficiency and delivering top-quality results as these have been highly valued in my past ventures. As a full-time remote worker, I pledge commitment to streamlined workflows and timely communication which will help ensure that your project stays on track while freeing up time for you to focus on strategic priorities. Let's work together to transform your challenges into achievements!
$2,000 USD in 30 days
3.3
3.3

Hi - Truong here "ASP.NET LEGACY MODERNIZATION + REACT" — you need someone who can keep the existing .NET systems stable while moving the platform forward I’d approach the legacy side conservatively: understand the existing Web Forms/MVC/WCF dependencies first, then expose or modernize services through ASP.NET Core without forcing risky rewrites. On the React side, I’d keep components and API boundaries clean so new features can be added without increasing the legacy burden. The difficult part is usually the boundary between old and new systems, especially shared authentication, database access, and business rules. I’d map those dependencies before changing production code. Which legacy stack is currently the largest part of the platform: Web Forms, MVC, or WCF?
$1,500 USD in 1 day
2.4
2.4

Mixing legacy .NET Web Forms with new React components often leads to duplicated state handling. I'll isolate the UI with an API layer built in ASP.NET Core, letting React talk to clean endpoints while the old Web Forms stay untouched. From there I can refactor the WCF services into async Web API calls as part of the migration plan. A common mistake is to rewrite legacy code line by line instead of wrapping it behind adapters, which stalls progress. By adding a thin ASP.NET Core service that proxies the old WCF calls, you keep the system stable while new React features roll out. You can expect a smoother transition, fewer production bugs, and a codebase that gradually moves toward .NET 6 without downtime.
$1,500 USD in 4 days
1.6
1.6

Hey, If you're not happy, you don't pay. I have extensive experience in front-end development using React and would be a valuable addition to your team as a Full-Stack Developer, proficient in maintaining and enhancing legacy .NET Framework applications while designing and building modern ASP.NET Core services and user-facing features in React. I'd love to share similar work I've done in my portfolio. Best, Kyle
$2,250 USD in 7 days
1.4
1.4

Hi There!!! i understand you are looking for a full stack developer comfortable bridging legacy .NET Framework applications with modern ASP.NET Core services, while also building responsive React features and helping guide the platform's modernization. Maintaining older Web Forms or MVC systems while refactoring toward .NET Core and improving overall architecture is work my team approaches carefully, keeping production stable throughout the transition rather than rushing changes. Building clean React components with proper state management, working across REST APIs and SQL Server, and collaborating closely with product and design teams fits well with the day to day scope you have outlined. Would love to hop on a quick call to understand your current codebase and priorities for the first modernization milestones. Best Regards, Hussain Ahmed Quick questions for you, Roughly what portion of the current codebase is still on legacy .NET Framework versus ASP.NET Core? Is there an existing CI/CD pipeline in place, or is that part of the modernization scope? Which legacy modules are the highest priority to refactor first?
$1,500 USD in 10 days
1.5
1.5

I can create and modernize your full-stack .NET platform with ASP.NET Core APIs, legacy .NET migration, React UI, SQL Server, REST, testing, and production support, plus 2 months free support. Ready to start immediately.
$1,500 USD in 7 days
0.0
0.0

Hi, I’m interested in helping maintain and modernize your platform across legacy .NET, ASP.NET Core, and React. I’m comfortable working with existing codebases, understanding unfamiliar architecture, fixing production issues, and delivering clean, maintainable features without disrupting critical systems. My approach would be: 1. Review the existing legacy .NET Framework applications and identify areas that can be safely improved or migrated. 2. Build and maintain ASP.NET Core APIs/services using clean architecture and REST principles. 3. Develop responsive React features with reusable components and proper state management. 4. Work with SQL databases, Git workflows, API integrations, testing, and debugging across the stack. 5. Contribute to modernization, documentation, code reviews, and CI/CD improvements where required. I value clean code, clear communication, and practical solutions, especially when working with systems that combine legacy and modern technologies. I’m available to start and can work full-time remotely. I’d be happy to review your current architecture/codebase and discuss the first priorities.
$1,500 USD in 7 days
0.0
0.0

Hello, I’m Adam, a Senior Full-Stack Developer with over seven years of experience building, maintaining, and modernizing scalable web applications. I understand that this role requires someone who can support critical legacy .NET systems while gradually improving the platform with ASP.NET Core and React. My approach is to preserve existing functionality, document dependencies, add tests around important workflows, and modernize components in safe stages. My relevant experience includes: * C# and .NET Framework * ASP.NET MVC, Core, and REST APIs * React, TypeScript, hooks, and state management * SQL Server and relational databases * Legacy code analysis and migration * Unit testing, debugging, and code reviews * Git, CI/CD, AWS, and Azure * Technical documentation and Agile teamwork I write clean, maintainable code and can work independently across unfamiliar codebases. I also communicate clearly with product managers, designers, and engineering teams. I’m available full-time and comfortable with the stated salary range of $1,500–$2,000 per month. Which legacy technology currently requires the most attention: Web Forms, MVC, or WCF? Best regards, Adam
$1,500 USD in 7 days
0.0
0.0

Here! Hello there, I’m a full stack web developer (backend & frontend) with 6 years of professional experience over 600 projects done. I create all kinds of websites with a strong focus on building clean, modern and responsive websites that align with your specific business goals. I work with a solid stack of technologies including HTML5, CSS3, Flexbox, Bootstrap, JavaScript, React, C#, ASP .NET and MS SQL, which allows me to create professional, user-friendly interfaces and robust, secure back-end solutions. Whether you need a modern, fast, secure, and responsive websites, business websites, e-commerce stores, landing pages, booking platforms, website application’s, admin dashboards, REST APIs, authentication, payment integration and database driven solutions. I prioritize performance, clarity of layout, smooth user experience. I also pay close attention to maintainability, so your site can be updated and expanded easily over time. I’m committed to clear communication, meeting deadlines, delivering a solution that feels professional, reliable and price affordable. I'm waiting for your answer Best regards, Jure
$1,500 USD in 4 days
0.0
0.0

Hi! I am a Senior Software Developer with extensive experience in both legacy and modern .NET applications, including ASP.NET Core. I have successfully maintained and modernized web applications in previous roles, ensuring a seamless transition from older frameworks while enhancing user-facing features. One project involved refactoring a legacy system built on .NET Framework, migrating functionalities to ASP.NET Core, and improving the overall architecture, which resulted in a more responsive and maintainable application. I am confident in my ability to deliver high-quality, well-tested code and can effectively collaborate with your team to ensure smooth development processes. To better understand your requirements, could you please share which specific legacy applications will need immediate attention? Additionally, what is your timeline for the modernization efforts? I would love to chat further about how I can contribute to your project. Best regards, Jay
$1,500 USD in 7 days
0.0
0.0

Hi, You’re looking for someone who can work comfortably between legacy .NET systems and modern applications without disrupting critical functionality while gradually moving the platform forward. That balance between maintaining existing systems and improving them is what stood out to me in your project. I have 7+ years of experience working across software development and quality engineering, with hands-on experience around React, Node.js, APIs, databases, CI/CD, and complex SaaS platforms. I’m comfortable understanding unfamiliar codebases, troubleshooting issues across the stack, validating API integrations, and working closely with developers and product teams to deliver reliable features. For your platform, I can help with: * Maintaining and troubleshooting existing applications * Building and validating REST APIs and modern services * Working with React-based user interfaces * Supporting legacy-to-modernization efforts * Database and integration testing * Git-based development workflows and CI/CD * Identifying production issues and driving them through to resolution I focus on understanding the existing architecture first, then making changes that are safe, maintainable, and aligned with the longer-term modernization plan rather than simply adding another layer of complexity. Would you be open to sharing a little about the current .NET Framework stack and which parts you’re planning to modernize first?
$2,000 USD in 30 days
0.0
0.0

When legacy .NET Web Forms share the same session state with new React hooks, subtle race conditions can appear during concurrent updates. I'll isolate the session handling by moving shared data into a stateless API layer and let React fetch fresh values via short-lived tokens. That keeps the old code running while the front‑end gets reliable real‑time sync without touching the core business logic. A common pitfall is assuming WCF services will scale automatically when wrapped in ASP.NET Core, but they often hide tight coupling to old config files. I'd refactor those services into thin controllers that delegate to the same business layer, then add unit tests to catch hidden dependencies early. Ready to start immediately and keep both legacy and new features stable while the migration progresses.
$1,500 USD in 4 days
0.0
0.0

Hi, after reviewing the requirements carefully, I am interested in this Full Stack Developer role. I have strong experience with backend development, REST APIs, React, databases, Git, and modern software architecture, and I am comfortable working across existing codebases and modernizing legacy systems. I can work independently on feature development, bug fixing, API development, frontend improvements, and production issues while maintaining clean and maintainable code. I am also comfortable collaborating with teams and following established development workflows. I am available for long term full time work and would be happy to discuss my experience and availability.
$1,500 USD in 30 days
0.0
0.0

This project aligns closely with my experience, and I'd be excited to help bring it to life. I have a strong background in both legacy .NET Framework applications and ASP.NET Core, which will enable me to maintain and modernize your software platform effectively. While I am new to Freelancer, I have tons of experience and have done other projects off site. I’m particularly interested in the challenge of refactoring legacy code and improving overall architecture, as mentioned in your listing. My hands-on experience with React also positions me well to develop responsive, user-friendly features. I’d be happy to discuss your project further or provide a quick draft to demonstrate my approach. I would love to chat more about your project! Regards, Bester Devenier
$2,250 USD in 7 days
0.0
0.0

Seattle, United States
Member since Aug 6, 2026
$1500-3000 USD
$1500-3000 USD
$750-1500 USD
$750-1500 USD
$1500-3000 USD
₹12500-37500 INR
₹5000-10000 INR
₹1500-12500 INR
$30-40 USD
$250-750 USD
₹750-1250 INR / hour
₹100-400 INR / hour
₹1500-12500 INR
₹75000-150000 INR
$10-10000 USD
$1500-3000 USD
$15-25 USD / hour
$30-250 USD
$20-250000 AUD
€15000-25000 EUR
₹600-1500 INR
$25-50 USD / hour
$250-750 USD
$1500-3000 USD
$30-250 USD