A CS file is a source code file written in C# (pronounced "C Sharp"), an object-oriented programming language created by Microsoft for use with the .NET Framework. It is used for developing a range of applications, from simple desktop programs to applications for distributed environments.

CS file open in Adobe Dreamweaver CC 2019 CS files are often edited with Visual C#, a component of Microsoft Visual Studio. But, they can also be edited with a variety of other source code editors that feature syntax highlighting. You can even open CS files using a text editor bundled with Windows or macOS, such as Micorosft Notepad++ or Apple TextEdit. However, plain text editors are not good options for editing the files since they do not support the syntax structure. NOTE: When C# programs are compiled, they can then be run by the Common Language Runtime (CLR), which is included with the .NET Framework.