This article showed how to create a GUI in Windows Forms. Only three controls were used: Label, TextBox, and Button. However, there are many more, and I encourage you to examine documentation for the Windows.Forms namespace to learn about the others. If you don't have Visual Studio.NET, use the WinDes utility in the .NET Frameworks SDK, which has similar functionality.
Besides the focus on GUI functionality, you also learned bits about more C# language features such as inheritance, delegates, and events. The string type was introduced, and I provided an example of how to perform custom string formatting.
In the next article of this the code in this article will be reused but modified slightly, as I show how to create a Web service using Visual Studio.NET.