To put it bluntly the .NET Framework class library is just plain huge. I see in the future several books devoted solely to describing all the interfaces, structures, enumerations, classes, methods, variables, and so on that are contained within this library. One chapter like this one could never do it justice. The goal instead for this chapter is to focus on giving you a head start in learning how to navigate through this massive library.
Even though the library is big, it is well organized and (gasp!) well documented. Once you understand the basics of how the library is organized, it will be easy for you to locate what you are looking for. It should also be quite simple to figure out if what you are looking for is not included in the library.
You will just briefly touch upon the contents of the class library here. In the following chapters, you will delve deeper into many specific areas in the library.