03 Projects Lecture2

8/8/2019 03 Projects Lecture2

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Review: Visual Studio &

Programming

A computerprogram consists of instructions

readable by the computer which direct its

operations In modern development, programs begin as

instructions readable by (trained) humans

And end up as instructions readable by the

computer


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Review: Visual Studio &

Programming (cont.)

Programs consist of many parts

Visual Studio and Visual Basic support:

Authoring the component parts of the programs Managing the program parts

Converting the parts you write into machine readable

format

Combining the parts you write with a huge collection ofpre-written instructions

Other tasks


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Projects

Projects may consist of many parts

Solutionmultiple programs

developed together

We will not use this

Projectone program

All elements

are optional

but it must

have at least

one

SOLUTION

PROJECT

(Program)

FORM CLASS MODULE MISC.


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ProjectsForms

Forms provide the

visualinterface for a

program Forms contain

Controls

Properties

Methods Events with code

Non-event code

Controls also contain Properties, Methods,

and Event Code


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Assignment Operations (cont.)

Examples

intQuantity = 123

places the value 123 into the variable intQuantity

stLastName = Jones

places the value Jones into the variable

stLastName

lblLastName.Text = stLastName

places the contents of the variable stLastName

(whatever they are) into the Text property of the

label control lblLastName


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Events

Forms, Controls, and Classes recognize

events

Events are predefined (or programmer

defined) actions against an object Ifthe action occurs

Andifthereis code written fortheevent

Thenthe code willexecute

Three kinds of events for forms and controls Commonly used

Less commonly used

Almost never used


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Events (cont.)

Our first eventThe Click Event for a button

Private Sub cmdTransfer_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles cmdTransfer.Click

'***************************************************************

'* Places the contents of the txtTransfer text box

'* into the lblTransfer label text property'***************************************************************

lblTransfer.Text = txtTransfer.Text

End Sub

cmdTransfertxtTransferlblTransfer


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Events (cont.)

Event Arguments are created automatically and are only used for

advanced purposes

The procedure name and Handles expression are also createdautomatically

The event procedure header (what we are seeing here) is actually

created as one longline

Use the line continuation character to break it into twophysicallines

But still treated as one logicalline



Name of the event procedureLine continuation character

Event Arguments

Control and event that triggers the code


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Creating Event Procedures

Default Events Double-clickinga control or form in design

view creates the template for the default

event

Form: Load event

Button: Click event

Text Box: TextChanged event

Label: Click event Check Box & Radio Button: CheckChanged event

Combo Box & List Box: SelectedIndexChanged

Date Time Picker: ValueChanged event

NumericUpDown: ValueChanged event


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Other Events The at the top left corner of the code window

is a drop-down list of all objects on the form

Select the object whose event you want to program


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Other Events The right side of the code window contains a list of all

events supported by form/control selected in the left box

Selecting an event will create the event codetemplate for that control and event combination

Selected Object (left side)

Supported Events (right side)


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Other Events There can be a dizzying variety of events

supported for most objects

Most are for events so obscure that youwould never use them

Some are incredibly useful and you should

learn these over time


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Event ProceduresMultiple

Events You will often want the same code to run for

multiple events and/or controls

Add the control/event combination to theHandles expression

Private Sub txtTransfer_GotFocus

Handles txtTransfer.GotFocus, _

txtTransfer.Click, txtTest.GotFocus, txtTest.Click

End Sub


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Events (cont.)Private Sub txtTransfer_GotFocus(ByVal sender As Object, _

ByVal e As System.EventArgs) Handles txtTransfer.GotFocus, _


'***************************************************************

'* Handles the GotFocus and Click events of all text boxes on

'* the form.'* Automatically selects the contents of the text box so that

'* text can be replaced by typing

'***************************************************************

'* Create a text box object

Dim theTextBox As TextBox

'* Set the object to the control that triggered the event

theTextBox = sender

'* Select the text in the text box

theTextBox.SelectionStart = 0

theTextBox.SelectionLength = theTextBox.Text.Length

End Sub


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Properties

Visual design elements (forms and

controls) have properties that Control their behavior

Determine their appearance

Interact with the user

Properties may be set at

Design time

Run time In code

With user interaction

Both Design & Run Time


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Design Time Properties

Selecting an object in form

design mode gives access to

the objects properties in theproperties window

These properties will be the

default properties when a form

is first created Changes implemented in code

or by user interaction will persist

as long as the form is open or

until they are changed again


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Name Property

Every object has a Name property that

controls how your object is addressed in code

If the object is addressed in code you mustrename your object to indicate its:

Type (use a prefix)

Purpose of use (rest of the name) --

(e.g.txtTransfer) first-letter Capital

Youneednot renamelabels thatarenot

addressedon code


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Name Property (cont.)

Examples: lblLastName label

btnCancel or cmdCancel button

txtStreetAddress text box

dtpBirthDate date time picker

cboStyle combo box

lstDepartment list box

chkActive check box

rdoMaritalStatus radio button

frmCustomer form


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Important Form Properties

Accept Buttonbutton whose code will

execute if the Enter key is pressed

Cancel Buttonbutton whose code willexecute if the Escape key is pressed

Text*displays in the title bar

ControlBox*, FormBorderStyle, Maximize* &

Minimize* Buttons

StartPositionwhere form will initially load

SizeWidth & Height of the form

* Removing these will give a form with no title bar


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Common Control Properties

Textwhat is displayed in the control

Left / Topcoordinates in pixels from the

upper left corner of the form for the location

of the upper left corner of the control Width / Heightsize in pixels of the control

EnabledControl is always visible but can be

toggled to active or inactive & dimmed VisibleControl is visible or not

TabIndexsequence of the control in the

forms tab order


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Reading & Setting Properties

in Code

Properties may be read and set in code by

referring to them on the appropriate side of

an assignment operator (equal sign)



'***************************************************************

'* Places the contents of the txtTransfer text box

'* into the lblTransfer label text property

'***************************************************************

lblTransfer.Text = txtTransfer.Text

End Sub


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Properties in Code

Private Sub btnCatchMe_MouseMove(ByVal sender As Object, _

ByVal e As System.EventArgs) Handles btnCatchMe.MouseMove

'***************************************************************

'* What is going on here????

'***************************************************************

If Now.Second < 55 Then

If Now.Second < 30 Then

btnCatchMe.Top = 20Else

btnCatchMe.Top = Me.Height - btnCatchMe.Height - 30

End If

If Now.Second Mod 2 = 1 Then

btnCatchMe.Left = 20

Else

btnCatchMe.Left = Me.Width - btnCatchMe.Width - 20

End If

End If

End Sub


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Getting Stupid with Properties

You can do VERY stupid with appearance

properties

BackColor ForeColor

Font

Experiment and get it out of your system

Then stick with the defaults for your work in

this class


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Setting Tab Order

After the form is complete there is an easy to

set the whole forms tab order sequence

Select View | Tab Order from the menu

Click box by each control in the tab order you

want

If you screw it up start over

Set individual control Tab Stop properties to False

to exclude from the tab order


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Setting Access Keys

Putting an & in the Text property of a control

makes the followingletter the hot key for the

control.

Gives control focus if Alt-Letter is pressed

Executes button if it is a buttons Access key

Text boxes have no permanent Text property Set the hot key in a label that immediately

precedes the text box in the forms tab order

Labels cannot get focus but focus will shift to the

text box


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The Invoice Total form

Three types of controls

y A labeldisplays text on a form.

y A textbox lets the user enter text on a form.

y A button initiates form processing when clicked.


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A form after some controls have been added to it


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A form after the properties have been set


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Events

Private Sub txtTransfer_GotFocus(ByVal sender As Object, _

ByVal e As System.EventArgs) Handles txtTransfer.GotFocus, _


'***************************************************************

'* Handles the GotFocus and Click events of all text boxes on

'* the form.'* Automatically selects the contents of the text box so that

'* text can be replaced by typing

'***************************************************************

'* Create a text box object

Dim theTextBox As TextBox

'* Set the object to the control that triggered the event

theTextBox = sender

'* Select the text in the text box

theTextBox.SelectionStart = 0

theTextBox.SelectionLength = theTextBox.Text.Length

End Sub


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The Solution Explorer as a form file is being

renamed


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How to rename a file, project, or solution

y Right-clickon it in the Solution Explorer window and select theRename command from the shortcut menu. Or, select it in theSolution Explorer and press F2. Then, you can enter the new

name.

y Be sure NOT to change or omit the file extension when yourename a file.

y Remembertoothatusingathree-letterprefixtoindicatethecontentsofthefile (likefrmforaformfile)makesiteasierto

tellwhateachfilerepresents.

y Whenyouchangethenameofaformfile, VisualStudiowillalsochangetheNamepropertyfortheformandupdateanyreferenceswithintheexistingcodefortheform.


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How to save a file, project, or solution

y You can use the Save All button in the Standard toolbar or theSave All command in the File menu to save all files and projects

in the solution.

y You can use the Save button in the Standard toolbar or the Savecommand in the File menu to save a file, project, or solution. The

files that are saved depend on whats selected in the Solution

Explorer window.

y If a single file is selected, just that file is saved.y If a project is selected, the entire project and its solution are

saved.

y If a solution is selected, the entire solution and all its projectsare saved.

y If you try to close a solution that contains modified files, a dialogbox is displayed that asks you if you want to save those files .

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03 Projects Lecture2

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