C# borrows a bit from several popular languages, including C, C++, and Java. If you've programmed in Java, you'll find that, in C#, you can have a class name with a name that's not the same as the source file. Similar to Java, and unlike the C languages, C# doesn't have header files. Plus, you have the flexibility of either importing a namespace or specifying it fully when using a function like System.Console.Writeline. Again, this has the Java footprint all over it.

Also note that the C++ :: operator isn't required in C#. The task of referencing class members is accomplished with the dot (.) operator.

All the most important C# libraries are implemented in DotGNU. The library lineup includes the core System library that (among other things) contains classes for handling data types, the System.Collections library that helps define and traverse objects such as lists and arrays, System.IO for reading and writing streams and files, System.Net for network programming, System.Security for making your programs respect permissions, and, of course, System.Windows.Forms for creating GUIs.

However, some libraries are not directly available, such as System.Data, which provides classes to implement the ActiveX Data Object, or ADO for reading and writing data from various data stores such as databases. But you can use the ADO library via the ml-pnet package.

DotGNU-specific definitions for the packaged libraries are available online [4], although they are not complete, and it is possible that a function might not be defined there but available nonetheless. Some of the libraries do have missing constructs and methods, and you can also learn more about these elements online [5]. However, this information might not be up to date.