Creating Custom Controls

1. Creating Custom Controls

2. 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.

3. 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

4. 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)

5. 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

6. MyListBox Control • Able to show three types of list. • Property: • Type: Fruits, Digits, Letters • SelectedItem • Method: • CreateList • Event • SelectedEvent

7. 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

8. 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.

9. 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

10. TimeZone Control • A form that displays time in the four time zones. • Property: • Zone • Method: • ShowTime • Demo: TestTimeZone/TimeZoneAsProj

11. TimeZone Control Code Public 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

12. 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 Sub End Class

13. 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

14. 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

15. ValidDate Control Code Public 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

16. 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

17. Using DateTime Picker • Properties: • MaxDate • MinDate • Value: Selected date • One year appointment: • DateTimePicker1.MaxDate = DateAdd(DateInterval.Year, 1, Now) • DateTimePicker1.MinDate = Now • Event: • ValueChanged

18. 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

19. MyCalendar Control Code Public 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

20. 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 Sub End Class

21. 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

22. 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

23. 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.

24. 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

25. Graphics Example Private 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

26. 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

27. Adding Events to Controls Created with Code • AddHandler object.event, AddressOfeventhandler

28. 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

29. 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.

30. 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.

31. 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

32. 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 …

33. 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 = 0 Private 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

34. 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

35. 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.