A .NET .. developer uses Microsoft's .NET Framework .. to design, develop, and maintain software applications. They write code in languages such as C# and Visual Basic.NET, using the .NET libraries and tools. They build web, desktop, and mobile applications, and services for various domains. They also troubleshoot and debug any issues in the software, optimize the code for efficiency and performance, and may work with databases and data structures. They also work with other team members, like UI designers and testers, and follow the software development life cycle processes. They must stay updated about new .NET features and technologies.