BCA IPU VB.NET UNIT-III

FEDT VB.NET
F R O N T E N D D E S I G N T O O L
U S I N G
V B . N E T
P R E S E N T A T I O N B Y :
A N K I T V E R M A
( I T D E P A R T M E N T )
A N K I T V E R M A A S S T . P R O F E S S O R
U N I T - 3

Interface
 User interacts with application using well-defined user
interface.
 Two types of interface:
 CUI (Character User Interface)
 Commands for user interaction
 Not much user friendly
 E.g. Console Application
 GUI (Graphical User Interface)
 No need to remember commands
 Very easy to use & user friendly
 E.g. Windows Application
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WINDOWS FORMS

Windows Form
 Accept input from user & display information.
 Develop desktop based application.
 Provides full support of database connectivity & image
formats.
 System.Windows.Forms namespace support Form
Class.
 Title Bar, Menu Bar & Control Box are at top of form.
 Main area is called Client Area, surrounded by border.
 Form associated controls enriched with predefined
Properties, Methods & Events.

Windows Form
 Properties
 Define characteristics of controls like color, size, border etc.
 Methods
 Methods are defined by the action that an object can perform.
 Events
 These are actions that can be recognized by the objects.
 Event occur when the user, OS or application interact with
objects of program.
 They control the appearance & behavior of a form either at
design time or run time.

Windows Form: Properties & Methods
 Backcolor
 BackgroundImage
 FormBorderStyle
 None
 Fixed Single
 Sizeable
 Fixed Dialog
 Fixed 3D
 Fixed Tool Window
 Sizeable Tool Window
 MaximizeBox

 MaximizeBox
 MinimizeBox
 Text
 WindowState
 StartPosition
 CenterParent
 Manual
 CenterScreen
 WindowDefaultBounds
 WindowDefaultLocation

 Activate
 Close
 Show
 Refresh
 Hide
 Dispose

Windows Form : Example
 Example 1:

Windows Form : Example
 Example 2:

Windows Form: Events
 Activated
 Deactivate
 Click
 Load
 Closing
 Closed

MDI Forms
 Display multiple windows at same time.
 MDI form act as parent form or container for all other
forms, called MDI parent form.
 Contain Menu Bar, Tool Bar and Status Bar.
 E.g. Word
 By default, VB.NET support SDI application, where
only one window displayed at a time.
 E.g. Wordpad
 In MDI Application, child forms are displayed as
independent windows under parent MDI window.

MDI Forms
 Create a form & set IsMDIContainer property true, it
will act as container.
 Attach the menus to MIDI parent form.
 Click event of menu item, write:
Form2.Show()
 Add one more Form to project.
 Write code on load of Second Form:
Me.MdiParent = Form1
 Run the code & click on menu item.

MDI Forms

CONTROLS

Controls
 Major controls are:
 Label
 Linklabel
 Textbox
 Button
 Checkbox
 Listbox
 Radiobutton
 Combobox
 Groupbox
 Hscrollbar
 Vscrollbar
 Picturebox
 Timer
 ListView
 TreeView
 Panel
 ToolBar
 StatusBar

Controls : Properties & Methods
 Properties & Methods of controls are:
 Backcolor
 Forecolor
 Size
 Enable
 Locked
 Visible
 Location
 Font
 Maximum Size
 Minimum Size
 Hide
 Show
 Select
 Refresh

Label

Label
 Graphic control used to display text.
 User can’t edit text directly.
 Text properties can be set at Run Time / Design Time.
 It is in System.Windows.Form.Label class.
 Label can’t receive focus.
 Label Properties are:
 AutoSize
 BorderStyle
 Enabled
 Text Align
 Text

Label : Example
 Example:

Textbox

Textbox
 Accept input from user & retrieve data from database.
 Textbox can be Multiline, Editable or ReadOnly.
 It is subclass of System.Windows.Forms.TextBoxBase
Class.

Textbox : Properties & Methods
 Textbox Properties & Methods:
 Borderstyle
 MaxLength
 PasswordChar
 ReadOnly
 MultiLine
 Textbox Events:
 GotFocus
 LostFocus
 Click
 TextChanged
 KeyPress
 ScrollBars
 SelectedText
 TextAlign
 WordWrap
 AppendText
 Text
 Clear
 Select
 SelectAll
 Show
 Cut
 Copy
 Paste

Textbox : Example
 Example:

Link Label

Link Label
 Used to support hyperlinks.
 Derived from Label class.
 Link Label Properties:
 ActiveLinkColor
 LinkColor
 VisitedLinkColor
 LinkVisited
 Link Label Event:
 LinkClicked

Link Label : Example
 Example:

Button

Button
 Buttons are the controls which are used for click even.
 Button Properties:
 Text
 BackgroundImage
 ImageAlign
 TextAlign
 Button Event:
 Click

Radio Button &
Check Box

Radio Button
 Radio button is used to select any one option at time.
 These buttons are working in a group.
 GroupBox control is used to group the related controls
together.
 If we select a radio button from the group, the other
buttons can’t be select from the same group.

Radio Button : Properties & Event
 Radio Button Properties:
 Text
 AutoCheck
 Radio Button Event:
 Click

CheckBox
 Checkbox is used to set yes/no or true/false options.
 User can select one option at a time.
 When we select a checkbox, a right mark appears in it,
indicating that the box is selected.
 The image and text both can be displayed in the
CheckBox control.

CheckBox : Properties & Event
 CheckBox Properties:
 Text
 AutoCheck
 Checked
 ThreeState
 CheckState
 CheckBox Event:
 CheckedChanged

RadioButton & CheckBox : Example
 Example:

List Box &
Combo Box

ListBox
 Display list of items to user.
 User can select one or more items from list box.
 Scroll bar appears automatically if the list has too
many items.
 User can add items to control using Design Time or
Run Time.

ListBox : Properties & Events
 ListBox Properties:
 SelectionMode
 Sorted
 SelectedIndex
 SelectedItem
 MultiColumn
 Items
 Add
 ListBox Event:
 SelectedIndexChanged
 Clear
 Contains
 Insert
 IndexOf
 Remove
 RemoveAt

ComboBox
 It is used to display a drop down list of items.
 It is combination of a textbox in which user enters an
item & drop down list from which user selects an item.

ComboBox : Properties & Events
 ComboBox Properties:
 Sorted
 MaxLength
 SelectedIndex
 SelectedItem
 Items
 Text
 Add
 ComboBox Event:
 Clear
 Contains
 Insert
 IndexOf
 Remove
 RemoveAt

ListBox & ComboBox : Example
 Example:

Picture Box &
Timer Control

PictureBox
 Used to display images, handling images, editing
images.
 Image can be added at Run Time as well as at Design
Time.
 PictureBox Properties & Methods:
 Image
 BorderStyle
 SizeMode
 Load
 PictureBox Event:
 MouseDown

Timer Control
 Used to create periodic events.
 This control is not visible at Run Time.
 It work behind the scenes.
 TimerControl Properties & Methods:
 Enable
 Interval
 Start
 Stop
 TimerControl Event:
 Tick

PictureBox & Timer Control : Example
 Example:

HScrollBar &
VScrollBar

HScrollBar & VScrollBar
 Scroll Bars are Vertical & Horizontal controls that display a
Srcoll Box or Thumb that we can manipulate.
 The value of Scroll Bar changes when we drag the Thumb into
new position.
 ScrollBar Properties:
 Value
 Minimum
 Maximum
 LargeChange
 SmallChange
 ScrollBar Event
 ScrollValueChanged:

HScrollBar : Example
 Example:

Panel

Panel
 Panel is used to group other controls.
 It divide the form into different regions.
 Panel Control have scrollbars.
 Panel Control Properties:
 AutoScroll
 BorderStyle

Panel
 Example:

Menus

Menus
 Provide consistent way to group commands so that
user can access them very easily.
 MenuScript control is used to create menus.
 Menus are user friendly and interactive.
 Menu Item Properties:
 Checked
 DisplayStyle
 Enable
 ShortCutKeys
 Visible

Menus
 Example:

Exception Handling

Exception Handling : Types
 Types of Exception Handling
 Structured Exception Handling
 Structured Exception Handling is included in VB.NET
 E.g. When we open a file & file not exist, exception raised and
handled by system itself.
 Un-structured Exceptional Handling
 Un-structured Exceptional Handling of Visual Basic is still
supported in VB.NET.
 Exception class in system namespace is base class of
all Exceptions.

Exception Handling : Error Types
 Three types of Errors:
 Syntax
 Appear when we write the wrong Syntax.
 Easily fixed in .NET
 Runtime
 Appear only when we Compile & Run the code.
 Logical
 Appear when we use the application, but producing wrong result.

Exception Handling : System Defined
 System defined exceptions are:
 Exception
 Index Out Of Range Exception
 Null Reference Exception
 Argument Exception
 Arithmetic Exception

Exception Handling : Syntax
 Syntax:
Try
Catch [exception as type]
Catch [exception as type]
Finally
[finally statement]
End Try

Exception Handling
 Example:

User Defined Exception
 Example:

ADVANCED CONTROLS

List View

List View
 Used to display items.
 E.g. Window Explorer right pane
 User can view items in different modes:
 LargeIcon
 SmallIcon
 List
 Title
 Details

List View : Properties & Methods
 ListView Properties & Methods:
 AllowColumnReorder
 AutoArrange
 CheckBoxes
 Columns
 GridLines
 Items
 LabelEdit
 ListView Event:
 MultiSelect
 Sorting
 View
 ArrangeIcons
 Clear
 GetItemAt

List View : Example
 Example:

Tree View

Tree View
 Display hierarchy of nodes.
 Each node can have child nodes also.
 E.g. Window explorer leftpane

Tree View : Properties & Events
 TreeView Properties & Methods:
 CheckBoxes
 FullRowSelcet
 LabelEdit
 Nodes
 Scrollable
 SelectedNode
 GetNodeCount
 TreeView Events:
 AfterCollapse
 BeforeCollapse
 ShowLines
 ShowRootLines
 Sorted
 TopNode
 CollapseAll
 ExpandAll
 AfterExpand
 BeforeExpand

Tree View : Example
 Example:

ToolBar

ToolBar
 Placed after menu bar & consist of buttons.
 Different types of buttons can be created in toolbar.
 Standard Push Button
 Toggle Button
 Drop Down Button
 Separators
 Toolbar are usually docked along the top of its parent
window.
 Display tool tips when the user points the mouse
pointer at toolbar button.

ToolBar : Properties & Events
 ToolBar Properties & Methods:
 Appearance
 AutoSize
 Buttons
 Divider
 ShowToolTips
 TextAlign
 Wrappable
 ToolBar Events:
 ButtonClick

Status Bar

StatusBar
 Appear at bottom of window.
 Display panels or simple status bar to display single
message on bar.
 StatusBar Properties & Methods:
 BackgroundImage
 Font
 Panels
 ShowPanels
 StatusBar Events:
 PanelClick

Common Dialog Control

 Window application use standard dialog boxes for
common operations.
 These are implemented as standard control in toolbox.
 They are not visible at Run Time.
 Five types of dialog controls in toolbox under dialog
tabs:
 ColorDialog
 FolderBrowserDialog
 FontDialog
 OpenFileDialog
 SaveFileDialog

Common Dialog Control : Color Dialog
 Color Dialog is for selecting colors from list of colors.
 ColorDialog Properties & Methods:
 Color
 CustomColors
 FullOpen
 ShowHelp
 Reset
 ShowDialog

Common Dialog Control : Folder Browser Dialog
 Folder Browser Dialog is used to select the folder.
 FolderBrowserDialog Properties & Methods:
 RootFolder
 SelectPath
 ShowNewFolderButton
 Reset
 ShowDialog

Common Dialog Control : Font Dialog
 Font Dialog is similar to Font Dialog of MS Word.
 User can Select the font, style etc.
 FontDialog Properties & Methods:
 Color
 Font
 MaxSize
 MinSize
 ShowApply
 ShowColor
 ShowHelp
 Reset
 ShowDialog

Color Dialog & Font Dialog : Example
 Example:

Common Dialog Control :
Open File Dialog & Save File Dialog
 OpenFileDialog is used for selection of file to open.
 SaveFileDialog is used to select or specify the path of a
file in which current document will be saved.
 Properties & Methods:
 AddExtension
 DefaultExt
 FileName
 Filter
 MultiSelect
 OpenFile
 Reset
 ShowDialog
 ShowReadOnly
 Show Help

Folder Browser Dialog : Example
 Example:

Creating User Controls

Creating User Controls
 All windows form controls are reusable components
and they are used for window based application.
 We can create our own control other than existing.
 We can combine existing & our own custom control.
 Two main classes used for creating custom controls:
 Control Class
 Provide all basic functionality for the windows user.
 Handles user input through keyboard, mouse etc.
 User Class
 It is inherited child of control class.
 Provide empty control that can be used to create other control.

Creating User Controls : Types Of Controls
 There are three types of controls that can be created:
 Composite Control
 It is collection of Windows Form controls contained in single
container.
 Also called Constituent Controls.
 Extended Control
 In this, we derive an inherited control from the existing one.
 In this approach, we can retain all the functionality of parent control
and extend those functionality by adding our own custom properties
& methods.
 Custom Control
 This is new control from the beginning by inheriting from Control
Class.

Creating User Controls : Example
 Creating User Control (Button):

 Import User Control (Button):

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OBJECT ORIENTED
CONCEPTS

Object Oriented Concepts
 VB.NET is an Object Oriented Programming language
with features:
 Abstraction
 Encapsulation
 Polymorphism
 Inheritance
 It also support following:
 Overloading
 Overriding
 Structure
 Class
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Class
 Class is generally called a Blueprint or User Defined
Data Type.
 Class is collection of objects of similar type.
 Class consists of Attributes (Data Members) and
Behaviors (Member Functions), that are used by
Instances of that class.
 Class is an Abstract entity.
 Members of Class:
 Data Members, Properties, Methods & Events
 Class Access Specifiers:
 Public, Private, Protected, Friend & Protected Friend
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Object
 Objects are Real Time entity.
 They may present as Person, Place, Bank Account, Table of
Data, Item etc.
 It is Instance of class.
 Each object contain data & code to manipulate data.
 Two types of data members:
 Static or Class Member
 Members that apply to Class and called by their class names.
 Shared keyword is used with members.
 Instance or Object Member
 Members that apply to object.
 They referred by object name.
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Overloading & Overriding
 Overloading
 Provide different versions of a method that has same name &
different parameters.
 Parameters can be different from name, data type or ordering of
parameters.
 Overriding
 Replace inherited property or method.
 Overridden methods in subclass must be same as base class
method including name and parameters.
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Class Object Example
 Example:
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Constructor
 Special methods that allow control over initialization
of objects.
 Constructors are Procedures with name Sub New.
 Run when Instance of class is created.
 Explicitly called only from other Constructors.
 Parameterized Constructors:
 Parameters can be passed to constructors also.
 Shared Constructors can’t have parameters.
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Constructor Types
 Two types of Constructors:
 Shared Constructors
 Used to initialize Shared variables.
 Created using Shared keyword & shared with all instance of class.
 Not run more than one, during single execution of program.
 Explicitly Public access & we can’t write explicitly.
 We can’t initialize Instance variable in Constructor.
 Instance Constructors
 Initialize variable that are declared with Dim, Public, Private,
Friend, Protected etc.
 You can also access Shared variable within this.
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Constructor Example
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Destructor
 Special method used to release Objects from memory.
 Two types of Destructors:
 Finalize Method
 Called from the class or derived class, to which it belong.
 Called after last reference to an Object is released from Memory.
 .NET automatically runs Finalize Destructor.
 We can’t determine it’s execution, when an Object loses its scope.
 CLR calls this using system call called Garbage Collection.
 CLR periodically check for Object, if Object not used, this Destructor
is called automatically and Garbage Collection Starts.
 Finalize method is Overridden when we write our code Explicitly.
 Dispose
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Destructor
 Dispose Method
 Problem with Finalize Method is non deterministic nature.
 We can’t determine Finalize Method call explicitly.
 Dispose Method is called to release resource such as Database
Connection, File Handler or System Lock.
 Unlike Finalize Method, this is not called Automatically.
 Through code we have to call this Explicitly.
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 Example:
Protected Overrides Sub Finalize ( )
MsgBox (“Object Out Of Scope”)
EndSub

Structure
 It is User Defined Data Type.
 Structure combines Variables & Methods.
 Single Variable of Structure can hold different types of data.
 Structure can be declared Inside Class, Namespace, Module
or Another Structure.
 Access Specifiers are allowed for Structure & their members.
 Only Shared Members & Constants can be Initialized.
 Like Class, Structure have Constructors but only
parameterized.
 If we have Default Constructor, that must be declared as Shared one.
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Structure Example
 Example:
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Structure With Constructor Example
 Example:
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Class VS Structure
 Similarities:
 Both are User Defined Data Types.
 Both support members like Constructor, Variables, Constants,
Methods, Events etc.
 Both have Shared Constructors with or without parameters.
 Both can implement Interfaces.
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Class vs Structure
 Differences:
 Class can be Inherited from other Class, but Structure not.
 Class can have Instance Constructors with and without
parameters, but Structure only have parameterized.
 Class is Reference type, but Structure is Value type.
 Class allow initialization of members inside Class, but Structure
not allow inside initialization.
 Class have Private as default Access Specifier for all variables &
constants, but Structure have Public by default.
 Class Procedures can handle Events, but not in Structure.
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Method Overloaing

Method Overloading
 Overloading Methods have same name, but different
argument lists.
 Argument may differ in Type, Number or Order Of
The Parameter.
 Return type of Overloading Method can be Same or
Different.
 Method invoked depends upon the type of argument
passed.
 Overloading is example of Polymorphism.
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Method Overloading : Example
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Shared Members

Shared Members
 Shared keyword can be used with Constructor,
Methods & Variables.
 Shared methods can be overloaded like regular
methods.
 Shared variables create only one copy for all instances
of class.
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Shared Members : Example
 Example:
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Inheritance

Inheritance
 Inheritance refers to deriving new Class from existing Class.
 Derived Class is known as Sub Class and Parent Class is
known as Base Class.
 Derived Class inherits all Public & Protected Data Members,
Methods, Events & Constants.
 Constructor can’t be inherited.
 Types of Inheritance:
 Single
 Multi Level
 Hierarchical
 Multiple Inheritance only supported by using Interface
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Inheritance : Keywords
 Inherits
 Inherits keyword is used to inherit Class.
 MustInherit
 Indicate that Class must be inherited by other Class.
 It act as Base Class and similar to Abstract Class of Java.
 NonInheritable
 If class is marked NonInheritable, we can’t create its Sub Class
 MyBase
 Call parent Class Constructor and Parent Class Overridden Methods.
 It always refers the immediate Super Class.
 We can’t navigate to more than one level from the Child Class.
 MyBase.MethodName is not allowed in .NET
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Inheritance : Keywords
 Overloads
 Indicate that methods are Overloading.
 If Methods are in same class, no necessary to write this keyword.
 Overridable
 Allow method to be Overridden.
 Overrides keyword is used to override the Overridable Method.
 NotOverridable
 Prevent the method being Overridden.
 MustOverride
 Methods must be declared in MultiInherit Class.
 MustInherit
 Enable Abstract Class creation. Child Class must implement all Abstract
Methods, otherwise Child Class also must declared as Abstract Class.
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Inheritance : Example
 Example:
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Method Overriding

Method Overriding
 Sub Class is not only Inheriting but it can also give its
own implementation (override) for methods.
 All the methods can’t be Overridden.
 To allow methods to Overridden, Parent Class method
must use Overridable keyword.
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Method Overriding : Example
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Abstract
Base Class

Abstract Base Class
 MustInherit keyword is used to create Abstract Class.
 Contain Signature of method, that Derived Class can
implement in its own Class.
 We can’t create Object of it.
 Method with MustOverride keyword should not
contain any implementation.
 Class with even one MustOverride method, should be
declared as MustInherit.
 To implement method, Overrides keyword use in Sub
Class.
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Abstract Base Class
 If Sub Class is not implementing any one of Abstract
methods from Abstract Class, then Child Class must
be declared as Abstract one.
 Abstract Class can contain Non-Abstract Method also.
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Abstract Base Class : Example
 Example:
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Interface

Interface
 Interface defines Properties, Method and Events, called
members of Interface.
 Interface consist of only Declaration of Members but not
the Implementation.
 Only Class and Structure implement these data
members.
 Variables can’t be declared in the Interface.
 Single Class can inherit from only one Base Class, but
can implement any number of Interfaces.
 It support Multiple Inheritance.
 Implements keyword is used for their implementation.
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Interface Vs Class
 Interface can’t provide any implementation, whereas
Class can provide implementation to Methods.
 Interface can’t have Constructors, but Class can define
Constructors.
 A Class inherits from only one Class, but implements
multiple Interface.
28-11-2014 ANKIT VERMA 139

Interface : Example
 Example:
28-11-2014 ANKIT VERMA 140

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BCA IPU VB.NET UNIT-III

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