1. VB.NET User Interface Controls

2. VB User Interface Objects
Form
InputBox, MessageBox
Standard Controls:
TextBox, MaskedTextBox, List Box, Option Button, Check Box, CheckedListBox, Command Button, GroupBox, etc.
Menu:
MenuStrip, ContextMenuStrip
ToolStrip
ToolStripContainer
ToolTip
Others:
Containers
Components
Dialogs

3. Form Form is defined as a class. Methods:
Show, ShowDialog: Open a form
Activate, Focus: Make an opened form get focus
Hide, Close
Ex.
Me.Hide, Me.Close
Note: Closing a form is equivalent to delete a form.
Events:
Load, Activated, DeActivate, Closing, Closed

4. Multiple Forms Two forms: Form1, Form2 To Open Form2 from Form1:
Standard but troublesome way to open a form: Must create an instance of the form class by using the keyword New to access the form.
Dim f2 As New Form2()
f2.Show()
Open Form2 as a Modal form:
f2.ShowDialog() .

5. Demo: Problem with the Show method
Modeless form: Other forms can receive input focus while this form remains active.
FormName.Show()
Modal form: No other form can receive focus while this form remains active.
FormName.ShowDialog()
Demo: Problem with the Show method

6. Using the Default Instances of Forms to Open a Form
formName.Show, formName.ShowDialog
Always bring up the same underlying default instance of the form.
Example: Form2.ShowDialog

7. MessageBox MessageBox.Show(message) MessageBox.Show(message, Caption)
MessageBox.Show(message, Caption, Buttons)
Note:
1. In each format, arguments are positional and required.
2. This object returns a DialogResult data type. Possible values for a DialogResult data type are: Abort, Cancel, Ignore, No, None, OK, ReTry, and Yes. To test the return value:
Dim ReturnVal as DialogResult
ReturnVal=MessageBox(“hello”, …..)
If ReturnVal=DialogResult.OK…

8. Form Closing Event Example
Private Sub Form10_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
If MessageBox.Show("Are you sure?", "Warning", MessageBoxButtons.YesNo) = DialogResult.Yes Then
e.Cancel = False
Else
e.Cancel = True
End If
End Sub
Note: Event procedure arguments:
sender: object that triggers the event.
e: event object

9. InputBox InputBox(Prompt [,Title] [, Default] [, Xpos] [, Ypos])
Xpos is the distance from the left edge of the screen, and Ypos is the distance from the top of the screen. Both are measured in twips (1/1440th of an inch).
Note: The arguments are positional and optional. Enter a comma to skip an argument.
cityName = InputBox("Please enter city name:“, , “SF”)
If cityName = vbNullString Then
MessageBox.Show ("customer click cancel")
Else
Text1.Text = cityName
End If
Note: vbNullString is a VB constant representing null value. All VB constants are listed in Constants collection.

10. Text Box Useful properties Useful events BackColor, BorderStyle
ReadOnly
Enable
Visible
Password Character
Multiline
ScrollBar
Text
Useful events
TextChanged: default event
Validating

11. Input Validation Numbers are checked to ensure they are:
Within a range of possible values
Reasonableness
Not causing problems such as division by 0.
Containing only digits
IsNumeric
Texts are checked to ensure correct format.
Phone #, SSN.
Required field
Textbox:
Set CauseValidation property to true.
Use the Validating event:
Triggered just before the focus shifts to other control.

12. TextBox Validating Event IsNumeric function
Private Sub TextBox1_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating
If Not IsNumeric(TextBox1.Text) Then
e.Cancel = True
MessageBox.Show("enter digits only")
Else
MessageBox.Show("good")
End If
End Sub
Note: Why not use the TextChanged event?

13. MaskedTextBox To select a mask: Custom mask:
Click the smartTag and choose Set Mask, or
Use the mask property to choose a mask.
Custom mask:
Search Help
Example:
(???)-###

14. String Methods ToUpper, ToLower Length – Number of characters
TrimStart, TrimEnd, Trim
Substring(Start), Substring(Start, length)
IndexOf(SearchString), IndexOf(SearchString, Start)
0 based index
Case-sensitive
eName=“David”
Position=eName.IndexOf(“d”)
Return –1 if the searchString is not found.
Note: Text property of a Textbox has all the string methods.
Ex. TextBox1.Text.Substring(0,2)

15. Example: Extract the firstname and the lastname from a fullname
Dim indexSpace As Integer
Dim firstName, lastName As String
indexSpace = TextBox1.Text.IndexOf(" ")
firstName = TextBox1.Text.Substring(0, indexSpace)
lastName = TextBox1.Text.Substring(indexSpace + 1)
MessageBox.Show(firstName)
MessageBox.Show(lastName)

16. Validate SSN Format (Or Use MaskedTextbox)
Private Sub TextBox1_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating
Dim correct As Boolean = True
If Not IsNumeric(TextBox1.Text.Substring(0, 3)) Or _
Not IsNumeric(TextBox1.Text.Substring(4, 2)) Or _
Not IsNumeric(TextBox1.Text.Substring(7, 4)) Then
correct = False
End If
If TextBox1.Text.Substring(3, 1) <> "-" Or TextBox1.Text.Substring(6, 1) <> "-" Then
If correct Then
MessageBox.Show("perfect format")
Else
e.Cancel = True
MessageBox.Show("not correct format")
End Sub

17. Group Box It is a container control.
Controls in a Group Box should move with the box.

18. Radio Button
Radio buttons must be grouped together inside a container such as a GroupBox or a form.
When the user selects an option all other options in the same group are deselected.
Properties:
Checked: True/False.
Default button: Set the Checked property to true at the design time.
Events:
CheckedChanged

19. RadioButton Example 1
Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
If RadioButton1.Checked = True Then
MessageBox.Show("Check RadioButton1")
Else
MessageBox.Show("uncheck RadioButton1")
End If
End Sub

20. RadioButton Example 2 If radioButton1.Checked=true then
textbox1.text=“You select radio button 1”
ElseIf radioButton2.Checked=true then
textbox1.text=“You select radio button 2”
Else
textbox1.text=“You select radio button 3”
End If

21. Check Box
Check boxes do not belong to a group even when they are grouped in a Group Box.
Checked property and checkedChanged event

22. Check Box Example 1
Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
If CheckBox1.Checked = True Then
MessageBox.Show(“check chk1")
Else
MessageBox.Show("uncheck chk1")
End If
End Sub

23. Check Box Example 2 Dim msg as String Msg=“You choose “
If checkBox1.checked=true then
msg=msg & “check box 1”
End If
If checkBox2.checked=true then
msg=msg & “check box 2”
If checkBox3.checked=true then
msg=msg & “check box 3”
Note: Cannot put these three conditions in a If …ElseIf block.

24. List Box Useful properties Methods Event: SelectedIndexChange
Items: The items in the listBox. It is a collection strcture. Items can be entered at the design time or entered in code.
0-based index
SelectionMode: one or multi selection
SelectedItem(s)
MultiColumn
Methods
Add
Clear
Event: SelectedIndexChange

25. List Box Example
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
TextBox1.Clear()
TextBox2.Clear()
ListBox1.Items.Clear()
ListBox1.Items.Add("Apple")
ListBox1.Items.Add("Orange")
ListBox1.Items.Add("Banana")
ListBox1.Items.Add("Strawberry")
TextBox2.Text = ListBox1.Items.Count.ToString
End Sub
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
TextBox1.Text = ListBox1.SelectedItem

26. List Items Collections
Methods:
ADD: ListBox1.Items.Add("Apple")
Item: Retrieve an object from Items
ListBox1.Items.Item(Index) or ListBox1.Items(Index)
0-based index
Insert: ListBox.Items.Insert(Index, item)
Remove: Delete an object with a position index or key.
ListBox.Items.Remove(Item)
ListBox.Items.RemoveAt(Index)
Clear: ListBox.Items.Clear()
Count: Return the number of objects in a collection.
ListBox.Items.Count

27. Selected Item’s Value Demo: Select interest rate from a list box:
5% -> 0.05
Dim intRate As Double
Select Case ListBox1.SelectedItem
Case "5% "
intRate = 0.05
Case “6%”
intRate = 0.06
Case “7%”
intRate = 0.07
End Select

28. CheckedListBox ItemCheck event Multiple selections: CheckedItems
Private Sub CheckedListBox1_ItemCheck(ByVal sender As Object, ByVal e As System.Windows.Forms.ItemCheckEventArgs) Handles CheckedListBox1.ItemCheck
TextBox2.Text = CheckedListBox1.SelectedItem
End Sub
Multiple selections:
CheckedItems
CheckedIndices
GetItemChecked

29. Using CheckedIndices and GetItemChecked Properties
Dim i As Integer
For Each i In CheckedListBox1.CheckedIndices
MessageBox.Show(CheckedListBox1.Items(i))
Next
For i = 0 To CheckedListBox1.Items.Count - 1
If CheckedListBox1.GetItemChecked(i) = True Then
End If

30. ComboBox Allows the user to type text directly into the combo box.
Use the Text property to get entered item:
ComboBox1.Text
The index for an entered item is –1.
SelectedItem may be different from the Text property.
Search an item in the list: ComboBox1.Items.IndexOf(“search text”)
Found: return the index of the search text.
Not found: return –1.
How to add an entered item to the list?

31. Timer Timer Properties:
Enabled -- must set to True.
Interval
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick label1.Text = System.DateTime.Now.ToString
End Sub

32. Use a Timer to Close a Form
Dim counter As Integer = 0
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
counter = counter + 1
If counter > 100 Then
Me.Close()
End If
End Sub

33. Structured Error Handling
Try
result = Val(TextBox1.Text) / Val(TextBox2.Text)
TextBox3.Text = result.ToString
Catch except As DivideByZeroException
MessageBox.Show(except.Message)
Catch except As Exception
Finally
MessageBox.Show("I get exdecuted, no matter what")
End Try

34. MenuStrip Control
Add MenuStrip control and follow the TypeHere instruction.
Each submenu and each item on a submenu is represented by a MenuItem control.
Write an event procedure for each menu item.

35. Using One Event Procedure to Handle Many Events
Private Sub BtnClick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click, Button2.Click, Button3.Click
If sender.name = "Button1" Then
MessageBox.Show("btn 1")
ElseIf sender.name = "Button2" Then
MessageBox.Show("Btn2")
Else
MessageBox.Show("btn3")
End If
End Sub
Note 1: Controls’ Tag property
Note 2: Late binding