Creating Custom Controls

Overriding ToString Method

• Every class you create in VB.Net is derived from a built-in class named object.– Mscorlib/system/object

• The object class has a method named ToString method which returns a fully-qualified class name.

• This method is overridable.

Code Example

Public Class Person

Public SSN As String

Public FirstName As String

Public LastName As String

Public BirthDate As Date

Public Overrides Function ToString() As String

toString = FirstName & " " & LastName & "'s birthday is " & BirthDate.ToString

End Function

Overriding and Overloading GetHashCode Method

Public Overloads Overrides Function GetHashCode() As Integer

GetHashCode = CInt(SSN.Substring(0, 3)) Mod 10

End Function

Public Overloads Function GetHashCode(ByVal M As Integer) As Integer

GetHashCode = CInt(SSN.Substring(0, 3)) Mod M

End Function

Code Example:

Dim myPerson As New Person()

myPerson.SSN = TextBox1.Text

TextBox2.Text = myPerson.GetHashCode

TextBox3.Text = myPerson.GetHashCode(100)

Creating Custom Controls

• A customer control is a control that is designed by a programmer for a specific purpose. It is derived from the System.Windows.Forms.UserControl class.– Object Browser

• Two ways to create a control:– Windows Control Library Project

• Controls can be used in multiple projects.

– Add a new UserControl to an existing project.• Only in current project

MyListBox Control

• Able to show three types of list.• Property:

– Type: Fruits, Digits, Letters– SelectedItem

• Method:– CreateList

• Event– SelectedEvent

Creating MyListBox Control

• New Project/Windows Control Library• Design control’s appearance and add any

functionality you want.• Build the DLL:

– The DLL is saved in project’s Bin folder.

• Create a Windows project to test the control.– Right Click Windows Forms tab of the Tool Box and

choose Add/Remove Items– Click .Net Framework component– Click Browse to select the DLL

Testing Custom Controls

• Create and build the control.

• Keep the custom control project open, and go to Windows desktop to open a second Visual Studio window.

• In the second Visual Studio window, open a project to test the custom control.

Code Using MyListBox Control

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click MyListBox1.type = myListBox.myListBox.listType.Letters MyListBox1.createList() End Sub

Private Sub MyListBox1_selectedEvent() Handles MyListBox1.selectedEvent textbox1.text = MyListBox1.selectedItem End Sub

TimeZone Control

• A form that displays time in the four time zones.

• Property:– Zone

• Method:– ShowTime

• Demo: TestTimeZone/TimeZoneAsProj

TimeZone Control CodePublic Class TimeZone

Inherits System.Windows.Forms.UserControl

Enum tzone

Eastern = 1

Central

Mountain

Pacific

End Enum

Private sysTime As Date

Private tmZone As tzone

Public Property Zone() As tzone

Get

Zone = tmzone

End Get

Set(ByVal Value As tzone)

tmzone = Value

End Set

End Property

Private Sub TimeZone_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load tmZone = tzone.Eastern ‘Use control’s load event to assign initial value to control’s property End Sub Public Sub ShowTime() sysTime = Now If tmZone = tzone.Eastern Then lblE.Text = sysTime.ToLongTimeString lblC.Text = DateAdd(DateInterval.Hour, -1, sysTime).ToLongTimeString lblM.Text = DateAdd(DateInterval.Hour, -2, sysTime).ToLongTimeString lblP.Text = DateAdd(DateInterval.Hour, -3, sysTime).ToLongTimeString ElseIf tmZone = tzone.Central Then lblC.Text = sysTime.ToLongTimeString lblE.Text = DateAdd(DateInterval.Hour, 1, sysTime).ToLongTimeString lblM.Text = DateAdd(DateInterval.Hour, -1, sysTime).ToLongTimeString lblP.Text = DateAdd(DateInterval.Hour, -2, sysTime).ToLongTimeString ElseIf tmZone = tzone.Mountain Then lblM.Text = sysTime.ToLongTimeString lblE.Text = DateAdd(DateInterval.Hour, 2, sysTime).ToLongTimeString lblC.Text = DateAdd(DateInterval.Hour, 1, sysTime).ToLongTimeString lblP.Text = DateAdd(DateInterval.Hour, -1, sysTime).ToLongTimeString Else lblP.Text = sysTime.ToLongTimeString lblE.Text = DateAdd(DateInterval.Hour, 3, sysTime).ToLongTimeString lblC.Text = DateAdd(DateInterval.Hour, 2, sysTime).ToLongTimeString lblM.Text = DateAdd(DateInterval.Hour, 1, sysTime).ToLongTimeString End If End SubEnd Class

Code Using TimeZone Control

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

TimeZone1.Zone = TimeZoneControlLibrary.TimeZone.tzone.Pacific

TimeZone1.ShowTime()

End Sub

Create an Inherited User Control

• Create a user control from an existing control such as TextBox, Label, etc.

• Example: Create a control, called ValidDate, that looks exactly like a textbox, but it will validate the entry for a valid date.– Inherits from System.Windows.Forms.TextBox

– Properties: MaximumDate, MinimumDate with default value

– Event: InvalidDate event

ValidDate Control CodePublic Class ValidDate

Inherits System.Windows.Forms.TextBox

Public Event InvalidDate(ByVal message As String)

Private maxDate As Date = Now.Date.AddYears(1)

Private minDate As Date = Now.Date

Public Property MaximumDate() As Date

Get

MaximumDate = maxDate

End Get

Set(ByVal Value As Date)

maxDate = Value

End Set

End Property

Public Property MinimumDate() As Date

Get

MinimumDate = minDate

End Get

Set(ByVal Value As Date)

minDate = Value

End Set

End Property

Private Sub ValidDate_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Validating

If Not IsDate(Me.Text) Then

Me.SelectAll()

e.Cancel = True

RaiseEvent InvalidDate("Date not valid")

Else

Dim enteredDate As Date = CDate(Me.Text)

If enteredDate < minDate Or enteredDate > maxDate Then

RaiseEvent InvalidDate("Date out of range")

Me.SelectAll()

e.Cancel = True

End If

End If

End Sub

End Class

Using DateTime Picker

• Properties:– MaxDate

– MinDate

– Value: Selected date• One year appointment:

– DateTimePicker1.MaxDate = DateAdd(DateInterval.Year, 1, Now)

– DateTimePicker1.MinDate = Now

• Event:– ValueChanged

Create an One-Year Appointment Date/Time Picker Control

• This control contains a DataTimePicker to choose appointment date up to one year in advance, and buttons to choose time. This control exposes two properties:– SelDate– SelTime

MyCalendar Control CodePublic Class testCalendar

Inherits System.Windows.Forms.UserControl

Private hiddenDate As Date

Private hiddenTime As String

Public ReadOnly Property selDate() As Date

Get

selDate = hiddenDate

End Get

End Property

Public ReadOnly Property selTime() As String

Get

selTime = hiddenTime

End Get

End Property

Private Sub DateTimePicker1_ValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DateTimePicker1.ValueChanged hiddenDate = DateTimePicker1.Value End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click hiddenTime = "10 am" TextBox1.Text = hiddenTime End Sub Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click hiddenTime = "12 pm" TextBox1.Text = hiddenTime End Sub Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click hiddenTime = "2 pm" TextBox1.Text = hiddenTime End Sub Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click hiddenTime = "4 pm" TextBox1.Text = hiddenTime End Sub Private Sub testCalendar_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load DateTimePicker1.MaxDate = DateAdd(DateInterval.Year, 1, Now) DateTimePicker1.MinDate = Now End SubEnd Class

Creating Form Controls With Code

• Use the name space: System.Windows.Forms– Ex. Define a textbox:– Dim tryTxt As New System.Windows.Forms.TextBox()

• Set property value:– tryTxt.Location = New System.Drawing.Point(70, 70)– tryTxt.Size = New System.Drawing.Size(144, 20)

• Add to form’s Controls collection:– Me.Controls.Add(tryTxt)– Form Controls example:

• Dim o As Object

– For Each o In Me.Controls– MessageBox.Show(o.GetType.ToString)– Next

Example

Private Sub Form11_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Dim tryTxt As New System.Windows.Forms.TextBox()

tryTxt.Location = New System.Drawing.Point(70, 70)

tryTxt.Size = New System.Drawing.Size(144, 20)

Me.Controls.Add(tryTxt)

Dim tryButton As New System.Windows.Forms.Button()

tryButton.Location = New System.Drawing.Point(70, 100)

tryButton.Size = New System.Drawing.Size(100, 20)

Me.Controls.Add(tryButton)

End Sub

Graphics Basics

• Create a graphics object.

• Create a Pen or Brush object to draw with.

• Call the drawing methods from the Graphics object to draw.

Form’s Paint Event

• Each time a form is displayed, resized, moved, maximized, restored, the form’s Paint event is triggered.

• Use the Paint event’s EventArg or a form’s CreateGraphics method to create a graphics object.

• Objects: Point, Size, Shape

Graphics ExamplePrivate Sub Form2_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint

Dim penBlk As New Pen(Color.Black, 10)

Dim gr As Graphics = e.Graphics

gr.DrawRectangle(penBlk, 50, 50, 100, 20)

Dim gr1 As Graphics

gr1 = Me.CreateGraphics

Dim penRed As New Pen(Color.Red, 10)

Dim startPoint As New Point(70, 10)

Dim grSize As New Size(50, 20)

Dim shapeRect As New Rectangle(startPoint, grSize)

gr1.DrawRectangle(penRed, shapeRect)

End Sub

Creating an Array of Textbox with Code

Dim test(1) As System.Windows.Forms.TextBox

Dim pointX As Integer = 50

Dim pointY As Integer = 80

Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Dim i As Integer

For i = 0 To 1

test(i) = New System.Windows.Forms.TextBox()

test(i).Location = New System.Drawing.Point(pointX, pointY)

test(i).Name = "TextBox" & i.ToString

test(i).Size = New System.Drawing.Size(144, 20)

test(i).Text = test(i).Name

test(i).Visible = True

pointY += 50

Me.Controls.Add(test(i))

Next

End Sub

Adding Events to Controls Created with Code

• AddHandler object.event, AddressOf eventhandler

Private pButton(2) As Windows.Forms.Button

Private pointX As Integer = 0

Private pointY As Integer = 0

Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Dim I As Integer

For i = 0 To 2

pButton(i) = New System.Windows.Forms.Button()

pButton(i).Location = New System.Drawing.Point(pointX, pointY)

pButton(i).Name = "button" & i.ToString

pButton(i).Size = New System.Drawing.Size(15, 20)

pButton(i).Text = i.ToString

Me.Controls.Add(pButton(i))

AddHandler pButton(i).Click, AddressOf ButtonClickHandler

pointY += 20

Next

End Sub

Public Sub ButtonClickHandler(ByVal sender As Object, ByVal e As _

System.EventArgs)

MessageBox.Show(sender.name)

End Sub

Keyboard-Related Events

• KeyDown: When a key is pressed.

• KeyUp: When a key is released.– The event procedure receives a KeyEventArgs

argument.

• KeyPress: When a key is pressed and released (for regular keys-digits and letters).– The event procedure receives a

KeyPressEventArgs.

Event Argument Properties

• KeyEventArgs:• Alt• Control• Shift

– Return a Boolean value indicating whether Alt/Ctrl/Shift was down.

• KeyCode: A member of Keys enumeration specifying the key that was pressed.

• KeyPressEventArgs• KeyChar: The character of the key pressed.• Handled: A Boolean indicating whether the event was handled

by a KeyPressEvent procedure. If not handled, this event will be processed by the form as usual.

Filtering Textbox Input to Permit Only Digits and Hyphen Using the Handled Property

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress

Select Case e.KeyChar

Case "0" To "9", "-"

'Do nothing - permitted character

Case Else

e.Handled = True

End Select

End Sub

Keys Enumeration

Private Sub TextBox1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Textbox1.keydown

If e.KeyCode = Keys.Delete Then

…

Create 3 Buttons and Implement Delete KeyTestMyGrid/Form2

Public Class Form2 Inherits System.Windows.Forms.Form Private pButton(2) As Windows.Forms.Button Private pointX As Integer = 0 Private pointY As Integer = 0Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load pointX = 50 pointY = 50 Dim i, j As Integer For i = 0 To 2 pButton(i) = New System.Windows.Forms.Button() pButton(i).Location = New System.Drawing.Point(pointX, pointY) pButton(i).Name = "button" & i.ToString pButton(i).Size = New System.Drawing.Size(100, 50) pButton(i).Text = "Button" & i.ToString Me.Controls.Add(pButton(i)) AddHandler pButton(i).Click, AddressOf ButtonClickHandler AddHandler pButton(i).KeyDown, AddressOf Grid_KeyDown pointY += 70 Next End Sub

Private Sub Grid_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs)

If e.KeyCode = Keys.Delete Then

Dim index As Integer

index = sender.name.substring(6, 1)

Me.Controls.Remove(pButton(index))

End If

End Sub

Creating a MyGrid Control

• Properties:– Rows, Cols: Initialized to 2.– Cell(RowIndex, ColIndex)

• Methods:– AddRow– ReDimension

• KeyDown event: Delete a row by pressing the Delete key.