Chapter 3.1Controls

Programming In

Visual Basic.NET

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Controls in the Toolbox

Those controls that we will use in this class.

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The Name Property

• How the programmer refers to a control in code

• Name must begin with a letter

• Must be less than 215 characters long

• May include numbers and the underscore

• Use appropriate 3 character naming prefix

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Control Name Prefixes

Control Prefix Example button btn btnComputeTotal label lbl lblInstructions list box lst lstOutput text box txt txtAddress group box grp grpColor radio button rdo rdoGreen checkbox chk chkShirt

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Text Box (txt)

• Used for user input/data entry

• Text Property– What is displayed in text box– What user entered in text box

• TextAlign Property– Controls alignment of text in the Text Box

• Change Event

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TextBox Control – Properties

• BorderStyle - defines the border surrounding the text box• ForeColor, BackColor - defines the text color and

background color respectively• Enabled - controls whether the text box can get focus and

will respond to events• Locked - controls whether user can change the text

appearing in the text box• MultiLine - controls whether text will appear on multiple

lines• MaxLength - defines the maximum number of characters

that the user can enter into the text box

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TextBox Control – Properties

• Name - defines name used to reference control instance with code– Again, use a standard prefix of "txt"

• ScrollBars - defines whether vertical or horizontal scroll bars appear in text box

• Text - contains the text appearing in text box• TextAlign - justifies text within the visible region

of the control instance• X, Y, Height, Width properties define the position

and size of the control instance

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TextBox - Methods and Events

• Focus method sets input focus to a text box

• Enter event fires when text box gets focus

• Leave event fires when text box loses focus

• TextChanged event fires when the the textual contents change at run time– The event fires for each character typed

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Button (btn)

• Used to run/activate an Event Procedure• Click event• Properties

– Text – Change the text property to display text to user

– Image – change image to use a graphic button

– Forecolor – changes the color of the text displayed

– Backcolor – changes the color of the button

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Label (lbl)

• Used for– Output on a form– Identification of objects– Directions/Information

• Cannot by modified by user

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Label Properties

• Text – used to display text or instructions to the user

• Font – change font size, color, appearance• Image – use images to draw attention• Autosize – adjust the label object to text

entered into the text property• textAlign – aligns the text displayed on the

object

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Group Box (grp)• Used as containers for other controls such

as radio buttons and check boxes• Improves readability of form• Text Property

– What is displayed on the top edge of the group box

• Splits the form object into separate planes– allows several groups of radio buttons on one

form.

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Group box (grp)

• Group boxes must be added to the form before other objects are added to them.– You can not drag checkboxes or radio buttons

from the form to the group box– The group box must have the focus of the

cursor before you draw your other objects inside them• Editing handles must be visible

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Check Box (chk)

• Used for user input/data entry

• Allows the user to select or deselect 1 or more in any group

• Checked Property– Checked = True– Unchecked = False

• CheckChanged Event – default event

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Radio Button (rdo)• Used for user input/data entry• Allows the user to select only 1 in any

group• First create a group and then create each

radio button inside the group• Checked Property

– Checked = True– Unchecked = False

• CheckChanged Event – default event

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Picture Box (pic)• Displays/contains a picture/graphic• Image Property

– Complete path and filename of graphic– .bmp, .gif (including

animated), .jpg, .png, .ico, .emf, .wmf

• SizeMode Property– StretchImage causes graphic to be resized to match

the size of the control

• Visible Property

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Other Properties• BorderStyle Property –None, FixedSingle, Fixed3D

• Forecolor – changes the color of text inside object• Backcolor – changes the color of object• Textalign – aligns text property• Enable

– true (user can activate the object), – false (object us not available to user)

• Visible – True (object appears on form)– False (object is hidden at run time)

• TabIndex – set the order of the focus for controls on the form

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Properties and Methods

• Properties can be set at design time in the property box

• Or they be changed during program execution by statements in your code– txtHours.Text = "“ ‘ clears the content

• Methods are action performed on objects– txtHours.focus

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Selecting Multiple Controls

• SHIFT-Click or CTRL-Click to select/deselect multiple controls

• Use the mouse to drag a selection box around multiple controls

• To deselect all selected controls click elsewhere on the form

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Selecting Multiple Controls (cont.)

Multiple selected controls,observe selection handles.

Using mouse to drag a selection box around multiple controls

Starthere

Dragto here

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What Can be Done with Multiple Selected Controls?

• Use Format Menu or Layout Toolbar to – Align them to each other– Make same size– Modify the spacing between them

• Move them as a group

• Set their common properties

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Designing the User Interface

• To the user the Interface should be– Easy to understand– Familiar– Comfortable– Organized– Sans Serif Fonts are best, not boldface or large– Color Neutral Overall– Keyboard Accessible

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Keyboard Access Keys

• Also referred to as Hot Keys

• Underlined Letter

• User presses ALT + underlined letter

• Use Windows-Standard Keys

• Defined using Text Property

Text=&OK

Text=E&xit

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Default & Cancel Buttons

• Default Button– Identified visually on Form by its darker outline– Responds to ENTER key– Form's AcceptButton Property

• Cancel Button– Responds to ESC key– Form's CancelButton Property

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Focus

• One control on a Form always has the Focus

• Not all control types can receive the focus• TabStop Property (applicable only for controls

that are capable of receiving the focus)– Designates whether a control is allowed to

receive the focus; True or False

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Tab Order• User should be able to use TAB key to move the

focus through a form in an organized manner; top to bottom, left to right

• TabIndex Property– Number in tab sequence

– 0 for first control to receive the focus when the form loads

• In form’s graphic view – Use View Menu, Tab Order to set

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Setting TabIndex Property

• View menu, TabOrder

• Click on each control in sequence to set TabIndex property of controls automatically

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Form's Screen Location

• StartPosition Property– Manual– CenterScreen– WindowsDefaultLocation– WindowsDefaultBounds– CenterParent

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ToolTips

• Small label that is displayed when user places pointer on a control and pauses

• Usually used with Command Buttons

• Steps for creating ToolTips– Add a ToolTip Control to Form

• Appears in the Component Tray, pane at bottom of Form Designer where nondisplay controls are shown

– Set ToolTip on ToolTip1 Property of each control to the text of tip

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ToolTip Control

Component Tray

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txtName.Text = ""lblMessage.Text = ""txtCourse.Clear( )

Clearing Text Boxes & Labels

• Set Text Property equal to the Empty String– Empty String is 2 quotation marks with no space

between them ("")

• Use the Clear Method of a Text Box

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txtName.Focus( )

Resetting the Focus

• Places the Insertion Point in a Text Box

• Use the Focus Method

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radRed.Checked = TruechkBold.Checked = False

Checked Property of Check Boxes and Radio Buttons

• Selects/Deselects Check Box or Radio Button

• Set Checked Property– True = Checked, selected– False = Unchecked, deselected

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VB Color Constants

• ForeColor and BackColor Properties

• Use VB Color Constants from the Color Class

• View complete list in Help by using the keyword Color followed by a period

txtName.ForeColor = Color.AliceBluelblMessage.BackColor = Color.White

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With txtName.Visible = True.Text ="Lynne". Focus( )

End With

With and End With

• Change several properties at once in Code

• Will run more efficiently

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lblFullName.Text = txtFName.Text & " " & txtLName.Text

lblNote.Text = "Today's weather is " & txtWeather.Text & "."

Concatenation

• Think of it as "glueing" text strings together

• Example: txtFName contains First Name txtLName contains Last Name

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lblMessage.Text = txtFName.Text & "" & txtLName.Text & _", welcome to Aiken Technical College. Today is " & _txtToday.Text

Continuing Lines of Code

• For long lines of code it is more readable to continue them to the next line

• At the end of the line type Line Continuation Character, a Space followed by an Underscore