.NET allows using the same namespaces, libraries, and APIs for different languages:
C#;
Visual Basic;
Visual C++;
F#.
When a programmer creates a program in one of these languages, the first thing he needs to do is include the System. This allows you to organize the program code into logical blocks, combine and separate some functionality from the rest of the code. If there were no .NET, then we would have to create a separate System for each programming language, and this would already violate one of the main principles of programming: "Do not repeat yourself."