A C# Web API developer designs, develops, and implements web-based applications using the C# programming language and .NET framework. They create API services for client-server communication, ensuring seamless data transfer. They write clean, scalable code, troubleshoot software issues, perform testing, and optimize systems for performance and reliability. They also work with databases, handle API versioning, and manage authentication and authorization. Additionally, they collaborate with other developers, UX designers, and business analysts to meet project requirements. They also provide technical support, maintaining and updating existing APIs as needed.