VB Procedures

Procedures. Sub procedure: Private/Public Sub SubName(Arguments) … End Sub Private: Can only be accessed by procedures in the same form. Public: Can be accessed by procedures in other forms. To call a sub procedure SUB1 Call SUB1(Argument1, Argument2, …)

Function Private Function tax(salary) As Double tax = salary * 0.1 End Function –Or Private Function tax(salary) Return salary * 0.1 End Function

Creating a IsAlphaNumeric(string) Function IsNumeric: test a string IsDigit, IsLetter, IsLetterOrDigit: test a char –Char.IsLetterOrDigit(char)

Function IsAlphaNumeric(ByVal aString As String) As Boolean Dim i As Integer = 0 Dim AlphaNumeric As Boolean = True For i = 0 To aString.Length - 1 If Not Char.IsLetterOrDigit(aString.Substring(i, 1)) Then AlphaNumeric = False Exit For End If Next If AlphaNumeric = True Then IsAlphaNumeric = True Else IsAlphaNumeric = False End If End Function Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click If IsAlphaNumeric(TextBox1.Text) Then MessageBox.Show("textbox1 is alphanumeric") Else MessageBox.Show("textbox1 is not alphanumeric") End If End Sub

Call by Reference Call by Value ByRef –Default –The address of the item is passed. Any changes made to the passing variable are made to the variable itself. ByVal –Only the variable’s value is passed.

ByRef, ByVal example Private Sub Command1_Click() Dim myStr As String myStr = TextBox1.Text ChangeTextRef (myStr) TextBox1.Text = myStr End Sub Private Sub ChangeTextRef(ByRef strInput As String) strInput = "New Text" End Sub

Input, Output Arguments Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim sal, tax As Single sal = CSng(TextBox1.Text) Call CalTax(sal, tax) TextBox2.Text = tax.ToString End Sub Private Sub CalTax(ByVal Salary As Single, ByRef Tax As Single) Tax = 0.1 * Salary End Sub Can we pass the Tax ByVal?

Static Variables Static VariableName as DataType Static variables are local variables but are not destroyed when a procedure terminates. Their value are kept.

Static Variable Example Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Static clickCounter As Integer = 0 clickCounter += 1 If clickCounter > 3 Then MsgBox("Sorry, you can only click 3 times!") Button1.Enabled = False End If End Sub

Event Procedures Example: –Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click The Handles keyword –Procedure name may change Handling multiple events: –Private Sub AllButtons_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click, Button2.CLick

Using One Event Handler to Handle Events Generated by Many Controls Assume we have 3 buttons. Use the Handles clause in the event procedure to associate controls with the event procedure. We can assign a value for each control’s Tag property, or use control’s TabIndex property to determine which control generates the event.

Private Sub Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click, Button2.Click, Button3.Click If sender.tag = "1" Then MessageBox.Show("button 1 clicked") ElseIf sender.tag = "2" Then MessageBox.Show("button 2 clicked") Else MessageBox.Show("button 3 clicked") End If End Sub Note: VB IntelliSense will not show the Tag property after you type sender.

Early Binding/Late Binding Early binding: VB compiler knows the object’s data type. It enables the use of IntelliSense. Late binding: VB compiler can’t determine the type of object that we are calling. This occurs because the object is declared as Object data type.

Demo: Phone Simulator

Menu

Main Menu Control –Add MainMenu control and follow the TypeHere instruction. –Each submenu and each item on a submenu is represented by a MenuItem control. –Use an & to specify an access key in the caption. Ex. &File, Sho&s –Write an event procedure for each menu item.

Shortcut keys –Select the Shortcut key property in the MenuItem’s property window. –Select the Shorcut key from list. –Set ShowShortcut property to true. Separator bar –Right clock a menu item/Insert Separator Inserting, deleting a menu item –Right click and select the option. Rearranging menu items –dragging

Context Menu A context menu is a menu that displays when an object on the screen is right- clicked. Add the ContextMenu control (it is placed in a tray under the form). Right-click the control and choose Edit to create the menu. Use the object’s ContextMenu property to bind the object to the context menu.

Simple Text Editor Textbox’s properties, methods –Help –Object Browser System.Windows.Forms –Cut, Copy, Paste, Undo, SelectAll, etc. Menu: Undo, Copy, Cut, Paste, SelectAll, Search Clipboard: –Clipboard.SetDataObject(TextBox1.SelectedText) –Clipboard.GetDataObject()

FontDialog Control If FontDialog1.ShowDialog() = DialogResult.OK Then TextBox1.Font = FontDialog1.Font End If