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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: 40646265
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51 freelancers are bidding on average $2,006 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

Hi — Elias here from Miami. I see you’re looking for a full-stack developer skilled in ASP.NET, Legacy .NET, and React. It’s clear you want to build something robust and scalable. The real challenge here often lies in integrating these technologies smoothly while ensuring maintainability. A common concern with such setups is managing state effectively across various components, especially as the application grows. What usually matters most is designing a system that can adapt to future requirements without becoming a maintenance burden. My approach would involve creating a modular architecture, emphasizing clear separation of concerns. This way, we can facilitate easier updates and integrations down the line. I focus on stability and performance, ensuring the application can handle increased loads and user interactions seamlessly. I’ve previously worked on similar full-stack applications, balancing front-end and back-end requirements while implementing best practices in code quality and documentation. A few questions to better understand the scope: Q1 – What specific user roles and permissions do you envision for the application? Q2 – Are there any existing systems you need to integrate with? 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’m perfect for this role and can support the platform using PHP/Laravel + React instead of the .NET stack mentioned in the JD. I have strong experience building and modernizing Laravel APIs, React frontends, REST integrations, SQL databases, authentication, and scalable architectures, including working with existing/legacy systems and migrating them to modern solutions. Key skills: * PHP / Laravel * React / TypeScript * REST APIs * MySQL / SQL * Legacy Modernization * Authentication & RBAC * Git / CI/CD * Cloud Deployment * Performance Optimization * Bug Fixing & Maintenance I understand your requirement is primarily full-stack development and modernization, and I can deliver the equivalent architecture using Laravel + React rather than ASP.NET/.NET. Let’s Chat… Thanks!
$1,700 USD in 20 days
5.5
5.5

Integrated Technologies is a full-service R&D and product development company specializing in embedded systems, IoT, robotics, AI, PCB design, firmware development, software development and cloud-connected applications. We take products from concept to production, delivering reliable, manufacturable, and well-documented solutions. We are pleased to work on your project on monthly basis for upgrading the dev technology. Having an in house team of developers, the development time will be reduced ensuring best deliverables. Looking forward to work on the project. Best Regards Shahbaz.
$2,000 USD in 30 days
5.0
5.0

✋ Hi There!!! ✋ THE PROJECT GOAL: MODERNIZE LEGACY .NET SYSTEMS AND BUILD RELIABLE REACT FEATURES. 5 KEY MATCHES: 1. Strong C# and .NET experience, including legacy Web Forms, MVC and WCF. 2. ASP.NET Core Web API, MVC and REST API development. 3. React with hooks, reusable components and state management. 4. SQL Server, Git, testing and clean maintainable architecture. 5. Legacy migration, troubleshooting, CI/CD and cloud-ready development. Similar projects have been completed involving legacy .NET modernization, ASP.NET Core APIs, React dashboards, database integration and production issue resolution. <-- Questions --> 1. Which legacy .NET applications are currently the highest priority for modernization? 2. Is the existing React application using TypeScript and a specific state management library? Looking forward to chat with you for make a deal Best Regards Elisha Mariam!
$1,511 USD in 11 days
4.9
4.9

Hi, I’m interested in the full-time position. I have been working in software development since 2011 and I’m comfortable working across both legacy and modern codebases. I can work with C#/.NET Framework, ASP.NET Core, REST APIs, React, TypeScript, SQL databases, Git and deployment workflows, including maintaining existing applications while gradually modernizing them without disrupting production. I’m available for long-term remote work and can work independently on existing codebases as well as collaborate with your team on new features, debugging and migrations. Expected rate: $2500/month I’m available to start immediately and happy to discuss your current architecture, working hours/time-zone requirements and the first priorities for the role.
$2,500 USD in 30 days
4.3
4.3

You need a full-stack developer who can maintain legacy .NET applications while moving the platform forward with ASP.NET Core and React. I have 9+ years of full-stack experience building and modernizing production systems across backend and frontend stacks, including C#, React, APIs, databases, and cloud environments. I am comfortable working inside existing codebases, fixing production issues, and gradually improving architecture without disrupting business-critical features. At Marin Software, I worked on production systems using Python, AWS, real-time pipelines, and modern frontend visualization. I have also shipped enterprise web applications using React and backend services, with experience integrating APIs, handling data workflows, and building maintainable application structures. I can support legacy .NET Framework maintenance, ASP.NET Core API development, React feature work, SQL-based data handling, documentation, and modernization efforts. I would like to understand your current .NET version, migration roadmap, and team workflow.
$2,250 USD in 8 days
4.1
4.1

Hello, I’m interested in supporting your team as a Full-Stack Developer and can contribute across both legacy .NET systems and modern application development. My approach fits well with your need for someone who can maintain critical existing applications while helping modernize the platform. I can work across C#/.NET, ASP.NET Core APIs, React, SQL databases, REST services, Git workflows, and legacy codebases, with a strong focus on maintainability, testing, performance, and clean architecture. I can contribute to: • Maintaining and enhancing legacy .NET Framework applications • Building and extending ASP.NET Core APIs and services • Developing responsive React interfaces using modern component patterns • Refactoring and modernizing legacy applications toward current .NET platforms • SQL/database integration and optimization • Production troubleshooting and root-cause analysis • Code reviews, documentation, Git workflows, and collaborative development I’m comfortable entering unfamiliar codebases, understanding existing architecture, and making improvements without unnecessarily disrupting stable functionality. I’m available for remote full-time work and can align with your engineering workflow, priorities, and communication processes. I’d be happy to discuss your current stack, modernization roadmap, and the first priorities for the role. I look forward to contributing to the continued evolution of your platform.
$1,500 USD in 7 days
4.3
4.3

Hi there! Quick question: are you planning to keep the legacy .NET Framework apps running as-is long-term, or is modernization to .NET Core a priority you'd like to tackle first? 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 expertise in legacy .NET maintenance and React front-end development, I specialize in streamlining legacy systems and enhancing modern technologies for optimal user experiences. My experience includes transforming legacy systems to align with current business needs, balancing functionality with progressive enhancements. I excel in developing scalable solutions using ASP.NET Core for robust back-end services and React for intuitive front-end interfaces. Proficient in SQL databases, REST APIs, and Git, I streamline collaborative workflows and optimize project efficiency through proactive code reviews and best practices. Looking ahead, I am keen on leveraging cloud platforms like Azure or AWS, integrating CI/CD pipelines, and advancing into microservices architecture for system resilience and scalability. Together, we can fortify your software platform for sustained success in the ever-evolving digital landscape. Let's connect to explore how we can elevate your software platform collaboratively.
$2,700 USD in 5 days
3.0
3.0

Drawing from my extensive 8+ years of experience as a Full-Stack Developer, specializing in ASP.NET and React, your project resonates deeply with my skill set. Having encountered and maintained myriad legacy .NET Framework applications, I am accustomed to successfully implementing modernization strategies - pinpointing the right balance between keeping critical systems running while guiding their evolution. I can confidently undertake this responsibility for you. My forte extends to bridging old and new technologies, creating a seamless transition that aligns with current industry standards. Alongside managing .NET applications, I have designed and built scalable APIs using ASP.NET Core and created user-facing features in React. My meticulous approach ensures clean, well-tested codes that contribute to maintainable and highly performing applications Moreover, my collaborative nature will be an asset in your cross-functional team environment. I have actively participated in code reviews, scoped and delivered features alongside product managers, designers, and fellow engineers. Additionally, my well-rounded skills include CI/CD pipeline exposure as well TypeScript familiarity. I can confidently iterate and evolve your software platform while strictly adhering to the best practices that drive growth. Choose me for unparalleled expertise and a proven track record of delivering results that exceed expectations.
$1,500 USD in 15 days
2.9
2.9

Greetings, Bridging legacy .NET applications with modern ASP.NET Core and React is exactly the kind of full-stack work I specialize in. I have more than 15 years of experience with C#, .NET Framework, ASP.NET MVC/Web API, ASP.NET Core, React, SQL Server, and enterprise application modernization. I can help maintain and enhance your existing Web Forms/MVC/WCF applications while progressively modernizing services to .NET Core and building clean, responsive React features. I’m also experienced with REST APIs, design patterns, production troubleshooting, code reviews, Git-based workflows, Azure/AWS, CI/CD, and microservices. I’m comfortable working independently in unfamiliar codebases and taking ownership from investigation through implementation and production support. I have a question: Do you already have a modernization roadmap for the legacy applications, or would you like the developer to help identify which components should be migrated first? I am available for a detailed discussion and to start immediately Best Regards, Waqar H
$2,500 USD in 20 days
2.9
2.9

With more than 5 years of experience in professional software development particularly with C# / .NET, I am no stranger to bridging the gap between old and new systems - a skill that is crucial for maintaining, modernizing, and extending legacy frameworks. My expertise with ASP.NET Core, React, and SQL Server aligns perfectly with the role you described, as does my understanding of REST APIs and software design patterns. Additionally, my broad experience across industries and foreign markets ensures that I can adapt and work effectively across unfamiliar codebases. My proficiency in Git and collaborative development workflows makes me an excellent team player for your project. Furthermore, my knowledge of CI/CD pipelines and exposure to Azure & AWS not only match up perfectly with your Nice-to-Have list but also authenticates my ability to deliver projects securely and efficiently. My price point is certainly competitive - being neither too high nor too low, and reflects the value proposition that I bring to your table. Let's talk about how we can modernize your existing applications using .NET Core/5+, optimize architecture for seamless functionality, and enhance user experience through clean-coded, well-tested interfaces using React. I assure you this focus on quality will make a lasting impact on your business's growth.EXPANDING_PARENT
$2,250 USD in 5 days
2.6
2.6

Hi - Truong here "LEGACY .NET TO MODERN ASP.NET CORE + REACT" — you need someone who can keep the old system stable while moving new work forward. I’d first map the existing .NET Framework dependencies and API boundaries before changing them, so modernization doesn’t break production. New services can move to ASP.NET Core while React handles new UI work, with SQL and REST changes kept backward-compatible where needed. I’d also keep legacy migrations incremental rather than forcing a risky rewrite, with tests around the parts being changed. Which legacy stack is the biggest priority right now: Web Forms, MVC, or WCF? Looking forward to working with you.
$1,837 USD in 1 day
2.0
2.0

Hi There!!! i understand you need a full-stack developer to maintain legacy .NET applications, build ASP.NET Core APIs, and develop React front-end features. I HAVE ALREADY MODERNIZED LEGACY NET FRAMEWORK APPLICATIONS AND BUILT ASP NET CORE APIS WITH REACT FRONTTENDS. Services based on what you are looking for: * Legacy .NET Framework maintenance, refactoring, and migration to modern .NET Core * Scalable ASP.NET Core Web API development and relational database management * Responsive React user interface development with hooks and state management * Continuous architecture improvements, code reviews, and production issue resolution * Complete technical documentation and collaborative Git development workflows Let us open a chat to discuss your current codebase and modernization roadmap. Best Regards, Hussain Ahmed
$1,500 USD in 18 days
1.5
1.5

Hi, You need a full-stack developer who can maintain legacy .NET Framework while building ASP.NET Core APIs and React UI. I read the role carefully, including the Web Forms/MVC/WCF upkeep, modernization work, and production troubleshooting. I’m Jaiom, and my background covers C#/.NET and React full-stack work, plus writing clean services and maintainable front ends. In prior projects, I worked on bridging older code with newer APIs by refactoring and improving test coverage, which maps to your migration goals. Which legacy .NET Framework modules need the most immediate modernization?
$2,500 USD in 3 days
0.0
0.0

Hello, With over 16 years of experience under my belt, including exposure to the demanding world of full-stack development, I believe I'm an ideal fit for your team. I have hands-on expertise in all fronts you're seeking, ASP.NET Core, Legacy .NET, and React. Moreover, I possess a profound understanding of C#/.NET and SQL Server across various platforms, counting WCF, Web Forms, MVC. In terms of modernization and codebase maintenance - I've been there! My experience working on legacy applications will be incredibly valuable to the project at hand. I can not only help keep critical systems running but effectively guide their evolution as we migrate to .NET Core/5+ and improve overall architecture. With firsthand knowledge in automating CI/CD pipelines on cloud platforms like Azure or AWS, I can further streamline your processes. Additionally, my seniority extends beyond simple coding; after several years in the field, I developed a refined set of problem-solving skills which have allowed me to excel independently where others might struggle. In leading a large team for more than a decade, maintaining transparency and ensuring effective communication were paramount - two essential qualities that will effortlessly carry over into remote work. Thanks!
$2,500 USD in 1 day
0.0
0.0

Hi, This role is a strong match for my experience working across legacy .NET systems and modern web architectures. I’d focus on keeping the existing .NET Framework applications stable while progressively extracting business logic into clean ASP.NET Core APIs and building maintainable React experiences on top. >>> Project Key Points: Legacy Web Forms/MVC/WCF maintenance, ASP.NET Core APIs, React with hooks/component architecture, SQL Server, REST integrations, production troubleshooting, code reviews, testing, documentation and gradual modernization toward a cleaner architecture. Execution Plan: I’d first map the existing dependencies, business-critical flows and technical debt before changing core components. For modernization, I’d use a strangler-style approach where appropriate—introducing ASP.NET Core services around stable legacy functionality rather than attempting a risky full rewrite. On the frontend, I’ll build reusable React/TypeScript components with predictable state management and API boundaries. CI/CD, automated testing, logging and Azure/AWS deployment practices can be incorporated as the platform evolves. With 7+ years of full-stack development, I’m comfortable moving between legacy codebases, modern APIs, databases and production debugging without losing sight of long-term maintainability. Best regards, Prateek
$2,250 USD in 7 days
0.0
0.0

I understand you're seeking a developer adept at navigating both legacy .NET Framework and modern ASP.NET Core, with a proven ability to integrate these with React. My experience includes modernizing monolithic .NET applications by refactoring core components into microservices and building new React frontends that seamlessly consume these APIs, achieving similar goals of bridging existing infrastructure with future-ready solutions. My technical approach would involve an initial deep dive into your legacy .NET Framework codebase to identify critical modules for refactoring. I'd leverage tools like ReSharper and SonarQube for static analysis and code quality checks. For modernization, I'd propose migrating key functionalities to ASP.NET Core, utilizing C# and Entity Framework Core. The React frontend would be developed using functional components, hooks, and state management libraries like Redux or Zustand, ensuring a clean separation of concerns and efficient data flow from your backend services. Given the emphasis on maintaining legacy systems while modernizing, how do you currently prioritize which .NET Framework components are candidates for refactoring versus those that will remain in place? Additionally, what are your current deployment pipelines for both legacy and new services? I'm eager to discuss how my skills can directly contribute to your platform's evolution.
$2,592 USD in 21 days
0.0
0.0

With over 5 years of professional experience in C# / .NET, I am confident that my skills align perfectly with your requirements for this role. Having worked extensively on legacy .NET Framework applications, I have a solid understanding of how to maintain and enhance existing systems while gradually incorporating new technologies. I believe this ability of mine would complement your aim of modernizing your platform and extending its capabilities. Additionally, my proficiency in ASP.NET Core and React would enable me to design, build, and maintain the services and APIs necessary for your platform's growth. With exposure to Azure and AWS, I have also managed cloud-based solutions which may prove valuable during the migration work outlined in the job description. Moreover, my familiarity with CI/CD pipelines will ensure smooth and efficient deployment without compromising on quality. Lastly, my problem-solving skills and adaptability to different codebases position me not only as someone who can effectively maintain existing systems but also as an individual capable of taking these systems towards a newer architecture. My goal is to keep critical applications running seamlessly while facilitating their evolution. Let's partner together on this project to bring a balance between the old and new to create a sustainable future for your software platform. Najam SA!
$2,250 USD in 7 days
0.0
0.0

Seattle, United States
Member since Aug 6, 2026
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