A .NET . developer designs, develops, and maintains software applications using the .NET . framework from Microsoft. They write clean, scalable code using .NET programming languages such as C# and VB.NET, upgrade existing .NET websites and applications, provide technical support for web, desktop, or mobile applications, and collaborate with internal teams to produce software design and architecture. They also test software to ensure responsiveness and efficiency, troubleshoot, debug, and upgrade existing software, and use .NET frameworks to build server-side applications, providing a high level of performance for end-users. They usually work within a team of developers, under a project manager.