A Microsoft Visual Studio developer designs, tests, and develops software applications using the Visual Studio IDE. They write code primarily in C#, C++, or Visual Basic, and use .NET framework for development. Their tasks include debugging programs, creating user interfaces, building databases, and developing web, mobile, or desktop applications. They also interact with APIs and libraries, and ensure software performance optimization. They may work on various stages of software development, from initial concept to final testing, often collaborating with other developers, designers, and stakeholders. They are also responsible for updating and maintaining existing software.