This book describes version 3. 0 languages C#. It is divided into two parts .. Part I provides a detailed explanation of the C# language, including new features introduced in version 3. 0. This is the largest part of the book, which describes the keywords and properties of a given language, as well as the operations of input-output and file processing, reflection and preprocessor. Part II deals with the C # class library, which is also the . class library. NET Framework. This library is quite extensive, but for lack of space in this book it is simply impossible to describe it completely. Therefore, Part II focuses on the root library, which is located in the System. namespace. In addition, this part deals with collections, the organization of multi-threaded processing and network connection to the Internet, as well as the creation of applications based on forms from the subsystem Windows Forms. These are the parts of the larger class library that anyone programming in C#. uses.