Control is the base class of all UI controls in Windows Forms applications. It provides common properties for all controls, as well as common user-interface control behaviors, such as accepting user input through the keyboard or mouse and raising appropriate events.

Table 8-1 shows the list of some representative properties, methods, and events that you would most likely encounter. For the complete list, check out the Microsoft .NET SDK.

The Control class also provides behaviors, such as data binding, context menu, drag and drop, anchoring and docking, and properties, such as font, color, background, cursor, and so on.

A form in Windows Forms is similar in concept to a page in Web Forms. It is a container type of control that hosts other UI controls. You manipulate the properties of the Form object to control the appearance, size, and color of the displayed form. A Windows Form is basically a representation of any window displayed in your application.

A standard form contains a titlebar, which contains an icon, title text, and control box for the Minimize, Maximize, and Close buttons (see Figure 8-1). Most of the time, a form also contains a menu right under the titlebar. The working area of the form is where child controls are rendered. A border around the whole form shows you the boundary of the form and allows for resizing of the form. Sometimes, the form also contains scrollbars so that it can display more controls or larger controls than the size of the working area of the form.

Figure 8-1. An empty application

You can manipulate the form’s standard visual elements with properties such as Icon, Text, ControlBox, MinimizeBox, MaximizeBox, and FormBorderStyle. For example, if you want the title text of the form to read Hello World, you include the assignment formName.Text = "Hello World";. To have a form without the control box in the top right corner, set the ControlBox property to false. If you want to selectively hide the Maximize or the Minimize button in the control box, set the MaximizeBox or MinimizeBox property to false.

You can assign a menu to your form by setting the Menu property of the form with an instance of the MainMenu class. We will show you how to do this in Section 8.3 of this chapter.

Similar to Submit and Reset buttons in a web page’s form, a form will frequently include OK and Cancel buttons to submit or to reset the form. In Windows Forms, you can assign any button to the AcceptButton property of the form to make it the default button when the user hits the Enter key. Similarly, you can set up the CancelButton property to handle the Escape key.

The Form class supports a number of methods itself, along with the methods it inherits from the base class. Activate, Show, Hide, ShowDialog, and Close are a few of the imperative methods used in any form to control the window-management functionality of a form. As we get into the Section 8.3 later in this chapter, you will see these methods in action.

class MyCustomTextBox : TextBox
{
  // customization goes here
}

class MyCustomComposite : UserControl
{
  // Composite controls go here
}

The Application class provides static methods to start, stop, or filter Windows messages in an application. All Windows Forms applications contain a reference to this Application class. More specifically, all Windows Forms applications start with something like the following:

System.Windows.Forms.Application.Run(new MyForm(  ));

While this class provides other methods and properties beside the Run method, this method is really the only essential one. The rest of the methods (listed in the rest of this section) are low-level and not frequently used.

The Run method starts the application thread’s message loop. This method has two signatures. The first signature involves no parameters, which are normally used for non-GUI applications.

System.Windows.Forms.Application.Run(  );

The second signature takes a form as a parameter, as you can see from the first example. The form MyForm is the entry point to a GUI Windows Forms application.

Table 8-2 summarizes the Application class.

Figure 8-2 illustrates the hierarchy of Windows Controls in the System.Windows.Forms namespace. These controls are placed on the form to create Windows Forms applications and on a UserControl container to create UI Controls (similar to current ActiveX controls). This figure does not include the Application class.

Figure 8-2. System.Windows.Forms Windows Controls class hierarchy