Form Properties

Since every form is derived from the Form class, which itself is derived from the Control class, they have all the properties of the Control and Form base classes, of which there are about one hundred. Many of the most commonly used properties are listed in Table 5-1. These properties can either be set in Visual Studio .NET at design time or set programmatically at runtime.

Table 5-1. Form properties

Property	Value type	Description
AcceptButton	IButtonControl	Gets or sets the button on a form that is clicked when the user presses Enter, irrespective of which control actually has focus.
ActiveForm	Form	Static property (shared in VB.NET) that gets the currently active form. Returns null (Nothing in VB.NET) if there is no active form.
ActiveMdiChild	Form	Gets currently active MDI child. Returns null (Nothing in VB.NET) if there is no active form. Allows operations on MDI child forms from MDI parent form, or determination if any open MDI child forms.
AutoScroll	Boolean	If set true, the default, scrollbars will automatically display if any controls are outside the form's client region.
BackColor	Color	Gets or sets the background color.
CancelButton	IButtonControl	Gets or sets the button on a form that is clicked when the user presses Escape, irrespective of which control actually has focus.
ClientSize	Size	Gets or sets the size of the area of the form excluding the borders and titlebar.
ControlBox	Boolean	Gets or sets a value indicating if the system menu can be displayed and if the Close button (X) is displayed on the right end of the titlebar. The system menu is exposed by clicking on the titlebar icon if the Icon property is set, or by right-clicking on the titlebar if the Icon property is not set. The default is true.
DesktopBounds	Rectangle	Gets or sets the size and location of the form on the Windows desktop, using pixel-based desktop coordinates.
DesktopLocation	Point	Gets or sets the location of the form on the Windows desktop, using pixel-based desktop coordinates. Differs from the Location property in that it takes into account the taskbar, if any.
DialogResult	DialogResult	Gets or sets the return value from a form or dialog box displayed modally. Legal values are members of the DialogResult enumeration. This is covered in detail in Chapter 6.
FormBorderStyle	FormBorderStyle	Gets or sets the border style. In addition to appearance, the FormBorderStyle dictates whether the form will be resizable. The possible values of the FormBorderStyle enumeration are listed in Table 5-2.
Height	Integer	Gets or sets the height of the form in pixels.
Icon	Icon	Gets or sets the icon for the form. The icon is displayed in the control box of the form (if ControlBox property is set to true) and in the taskbar (if ShowInTaskbar is set to true).
MaximizeBox	Boolean	Gets or sets a value indicating if maximize button will be displayed in upper right corner of form on the titlebar. The default is true. If true, FormBorderStyle must be either FixedSingle, Sizable, Fixed3D, or FixedDialog. When the form is maximized, the maximize button automatically becomes a restore button.
MinimizeBox	Boolean	Gets or sets a value indicating if minimize button will be displayed in upper right corner of form on the titlebar. Default is true. If true, FormBorderStyle must be either FixedSingle, Sizable, Fixed3D or FixedDialog. When the form is maximized, the minimize button automatically becomes a restore button.
Modal	Boolean	Read-only value indicating if form is displayed modally using the ShowDialog method.
Opacity	double	Gets or sets the opacity level of the form, its border, and its controls, which can range between 1.00 (100 percent), the default value, and 0. If value is 0, the form is completely invisible and cannot be clicked on.
ShowInTaskBar	Boolean	Gets or sets value indicating if the form Text property is displayed in the Windows taskbar. Default is true.
Size	Size	Gets or sets both the height and width of the form.
SizeGripStyle	SizeGripStyle	Gets or sets one of three possible values that indicate the style of the sizing grip displayed at the lower-right corner of a form. The valid values are Auto, which displays the sizing grip as if the form is opened modally, Hide, which hides the sizing grip, and Show, which always shows the sizing grip.
StartPosition	FormStartPosition	Gets or sets the starting position of the form. Legal values of the FormStartPosition enumeration are listed in Table 5-3.
TopLevel	Boolean	Gets or sets value indicating the form has no parent form ( i.e., if true, it is either an SDI form or an MDI parent form). The default is true. This property works in concert with the Parent property. A non-top-level TopLevel form just disappears if the Parent property is not set to a value. Also, an exception is raised if you try to set TopLevel to true without first setting Parent to null.
TopMost	Boolean	Gets or sets value indicating that the form is displayed on top of all the other forms, even if it is not the active form. Typically used for modeless dialog boxes that should always be visible, such as alerts.
Width	Integer	Gets or sets the width of the form in pixels.
WindowState	FormWindowState	Gets or sets value of enumeration that indicates the state of the form. Valid values are Normal (the default), Maximized, or Minimized.

Table 5-2. FormBorderStyle enumeration values

Value	Description
Fixed3D	Nonresizeable, 3D border.
FixedDialog	Nonresizeable, dialog-style border.
FixedSingle	Nonresizeable, single line border.
FixedToolWindow	Nonresizeable, tool window border.
None	No border.
Sizable	Default value. Standard resizable border.
SizableToolWindow	Resizable, tool window border.

Table 5-3. FormStartPosition enumeration values

Value	Description
CenterParent	Center form within parent form.
CenterScreen	Center form within current display.
Manual	Location and size of form dictates its starting position.
WindowsDefaultBounds	Form at Windows default location with bounds determined by Windows default.
WindowsDefaultLocation	Form at Windows default location with dimensions specified in form's constructor.