Related Reading VB.NET Core Classes in a Nutshell By Budi Kurniawan, Ted Neward

The FCL provides a full set of graphics objects, such as the Color structure, the Brush class, the Font class, and the Graphics class in the System.Drawing namespace.

The FCL allows you to read the standard input, standard output, and standard error streams, as well as to access the file system, through classes like File, FileInfo, StreamReader, and StreamWriter in the System.IO namespace.

Through the Type class in the System namespace and classes like Assembly, Module, EventInfo, MethodInfo, and ParameterInfo in the System.Reflection namespace, the .NET FCL provides support for reading metadata (the data that describes particular program elements) at any time.

Through classes such as ObjRef, RemotingConfiguration, and RemotingServices in the System.Runtime.Remoting namespace, the .NET FCL adds support for remoting (calls that cross process or machine boundaries).

Interestingly, in the .NET Framework, strings are immutable. This means that simple operations such as string concatenation involve an enormous performance penalty. The StringBuilder class in the System.Text namespace makes it possible to perform string concatenation efficiently. The RegEx and Match classes in System.Text.RegularExpressions make it possible to perform regular expression searches on strings.

In previous versions of Visual Basic, threading was a factor that enormously impacted VB applications but over which the VB developer had no control. With classes like Thread, Mutex, and Monitor in the System.Threading namespace, the .NET FCL for the first time places threading under the direct control of the VB.NET developer.

The .NET FCL features a brand new data access technology, ADO.NET. It is represented by classes like the DataSet class in the System.Data namespace, the OleDbConnection, OleDbCommand, and OleDbDataReader classes in the System.Data.OleDb namespace, and the SqlConnection, SqlCommand, and SqlDataReader classes in the System.Data.SqlClient namespace.

The forms and controls that made Visual Basic the premier Rapid Application Development package for Windows have their equivalent in the .NET FCL. These classes, such as the Form class, the Button class, and the TextBox class, are found in the System.Windows.Forms namespace.

In addition to Windows controls, the .NET FCL features two sets of controls for web application development. HTML server controls execute on the server but otherwise correspond more or less directly to standard client-side HTML controls. They are found in the System.Web.UI.HTMLControls namespace. Web controls (also known as ASP controls) are server controls that abstract the functionality of controls in a web application. They are found in the System.Web.UI.WebControls namespace.

A web service is simply a function call over the Internet. The .NET FCL supports the development of web services through the types in the System.Web.Services namespace.