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.





Programming. NET Windows Applications
Programming .Net Windows Applications
ISBN: 0596003218
EAN: 2147483647
Year: 2003
Pages: 148
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