WinForms from Scratch

A typical Windows Forms application has at least one form. Without the form it's just an "application," which is pretty boring. A form is simply a window, the unit of the Microsoft user interface we've seen since Windows 1.0. One form in a WinForms application is typically the main form , which means that it is either the parent or the owner[1] of all other forms that may be shown during the lifetime of the application. It's where the main menu is shown, along with the toolbar, status bar, and so on. When the main form goes away, the application exits.

The main form of an application can be a simple message box, a dialog box, a Single Document Interface (SDI) window, a Multiple Document Interface (MDI) window, or something more complicated, such as the forms you're used to seeing in applications like Visual Studio .NET. These latter forms may include multiple child windows, tool windows, and floating toolbars.

If your application is enormously simple, you can implement it using the staple of any windowing system, the lowly message box

If you're new to C#, Main is the entry point for any C# application. The Main function must be a member of a class, and hence the need for MyFirstApp. However, the .NET runtime doesn't create an instance of the MyFirstApp class when our code is loaded and executed, so our Main function must be marked static . In this way, you mark a method as available without creating an instance of the type. The single line of real code in our first WinForms application calls the static Show method of the System.Windows.Forms.MessageBox class, which is really a long-winded way of saying we're calling a method on the MessageBox class contained within the System.Windows.Forms namespace. Namespaces are used extensively in the .NET Framework Class Libraries (FCL) to separate types, such as classes, structures, enumerations, and so on, into logical groupings. This separation is necessary when you've got thousands of Microsoft employees working on the FCL as well as hundreds of third parties extending it and millions of programmers trying to learn it. Without namespaces, you would need all kinds of wacky conventions to keep things uniquely named (as demonstrated by the existing Win32 API). However, as necessary as namespaces are, they're a little too much typing for me, so I recommend the C# using statement, as shown here: