Learn Visual Basic 6.0

3. Exploring the Visual Basic Toolbox

Example 3-1: Password Validation

1. Start a new project. The idea of this project is to ask the user to input a password. If correct, a message box appears to validate the user. If incorrect, other options are provided.
   
   
2. Place a two command buttons, a label box, and a text box on your form so it looks something like this:
   
   
   
   
   
   
3. Set the properties of the form and each object.
   
   

   Form1:	BorderStyle	1-Fixed Single
   	Caption	Password Validation
   	Name	frmPassword
   Label1:	Alignment	2-Center
   	BorderStyle	1-Fixed Single
   	Caption	Please Enter Your Password:
   	FontSize	10
   	FontStyle	Bold
   Text1:	FontSize	14
   	FontStyle	Regular
   	Name	txtPassword
   	PasswordChar	*
   	Tag	[Whatever you choose as a password]
   	Text	[Blank]
   Command1:	Caption	&Validate
   	Default	True
   	Name	cmdValid
   Command2:	Cancel	True
   	Caption	E&xit
   	Name	cmdExit

   
   Your form should now look like this:
   
   
   
   
   
   
4. Attach the following code to the cmdValid_Click event.
   
   Private Sub cmdValid_Click()
   'This procedure checks the input password
   Dim Response As Integer
   If txtPassword.Text = txtPassword.Tag Then
   'If correct, display message box
   MsgBox "You've passed security!", vbOKOnly + vbExclamation, "Access Granted"
   Else
   'If incorrect, give option to try again
   Response = MsgBox("Incorrect password", vbRetryCancel + vbCritical, "Access Denied")
   If Response = vbRetry Then
   txtPassword.SelStart = 0
   txtPassword.SelLength = Len(txtPassword.Text)
   Else
   End
   End If
   End If
   txtPassword.SetFocus
   End Sub
   
   This code checks the input password to see if it matches the stored value. If so, it prints an acceptance message. If incorrect, it displays a message box to that effect and asks the user if they want to try again. If Yes (Retry), another try is granted. If No (Cancel), the program is ended. Notice the use of SelLength and SelStart to highlight an incorrect entry. This allows the user to type right over the incorrect response.
   
   
5. Attach the following code to the Form_Activate event.
   
   Private Sub Form_Activate()
   txtPassword.SetFocus
   End Sub
   
   
6. Attach the following code to the cmdExit_ Click event.
   
   Private Sub cmdExit_Click()
   End
   End Sub
   
   
7. Try running the program. Try both options: input correct password (note it is case sensitive) and input incorrect password. Save your project.
   
   If you have time, define a constant, TRYMAX = 3, and modify the code to allow the user to have just TRYMAX attempts to get the correct password. After the final try, inform the user you are logging him/her off. You�ll also need a variable that counts the number of tries (make it a Static variable).

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