Page 49 - Open Soource Technologies 304.indd

Unit 3: Understanding Controls and Control Events

We want to display some text, say, "Welcome to TextBoxes", in TextBox1 when the Button is
clicked. The code looks like this:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e_
As System.EventArgs) Handles Button1.Click
TextBox1.Text = "Welcome to TextBoxes"
End Sub

Code to Work with PassWord Character

Set the PasswordChar property of TextBox2 to *. Setting that will make the text entered in
TextBox2 to be displayed as *. We want to display what is entered in TextBox2 in TextBox1. The
code for that looks like this:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e_
As System.EventArgs) Handles Button1.Click
TextBox1.Text = TextBox2.Text
End Sub

When you run the program and enter some text in TextBox2, text will be displayed as *. When
you click the Button, the text you entered in TextBox2 will be displayed as plain text in TextBox1.
Code to Validate User Input
We can make sure that a TextBox can accept only characters or numbers which can restrict
accidental operations. For example, adding two numbers of the form 27+2J cannot return
anything. To avoid such kind of operations we use the KeyPress event of the TextBox.
Code that allows you to enter only double digits in a TextBox looks like this:

Private Sub TextBox1_KeyPress(ByVal sender As Object,ByVal e As_
System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
If(e.KeyChar < "10" Or e.KeyChar > "100") Then
MessageBox.Show("Enter Double Digits")
End If
End Sub

Creating a TextBox in Code

Public Class Form1 Inherits System.Windows.Forms.Form
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As_
System.EventArgs) Handles MyBase.Load
Dim TextBox1 as New TextBox()
TextBox1.Text="Hello Mate"
TextBox1.Location=New Point(100,50)
TextBox1.Size=New Size(75,23)
Me.Controls.Add(TextBox1)
End Sub
End Class

LOVELY PROFESSIONAL UNIVERSITY 43