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Objects Oriented Programming Fundamental (OOP)

Creating the Employee Class

In this activity, you will become familiar with the following:

Creating a VB class definition file using VS
Creating and using an instance of the class from VB client code

Note: If you have not already done so, download the starter files from the Source Code area of the Apress

Defining the Employee Class

To create the Employee class, follow these steps:

Start VS. Select File > Open > Project
Navigate to the Activity6_1Starter folder, click the Act6_1.sln file, and click Open. When the project opens, it will contain a login form. You will use this form later to test the Employee class you create.
Select Project > Add Class. In the Add New Item dialog box, rename the class file to Employee.vb, and then click Open. VS adds the Employee.vb file to the project and adds the following class definition code to the file:
```
Public Class Employee
End Class
```

Enter the following code to add the private instance variables to the class definition file:

Private _empID As Integer
Private _loginName As String
Private _password As String
Private _securityLevel As Integer

Add the following public properties to access the private instance variables defined in step 4:

Public ReadOnly Property EmployeeID() As Integer
    Get
        Return _empID
    End Get
End Property

Public Property LoginName() As String
    Get
        Return _loginName
    End Get
    Set(ByVal Value As String)
        _loginName = Value
    End Set
End Property
Public Property Password() As String
    Get
        Return _password
    End Get
    Set(ByVal Value As String)
        _password = Value
    End Set
End Property
Public ReadOnly Property SecurityLevel() As Integer
Get
Return _securityLevel
End Get
End Property

Add the following Login method to the class definition:

Public Sub Login(ByVal loginName As String, ByVal password As String)
    LoginName = loginName
    Password = password
    'Data normally retrieved from database.
    'Hardcoded for demo only
    If loginName = "Raja" And password = "pheak" Then
        _empID = 1
        _securityLevel = 2
    ElseIf loginName = "Son" And password = "Khunpheakdey" Then
        _empID = 2
        _securityLevel = 4
    Else
        Throw New Exception("Login incorrect.")
    End If
End Sub

Select Build > Build Solution. Make sure there are no build errors in the Error List window. If there are, fix them, and then rebuild.

Testing the Employee Class

To test the Employee class, follow these steps:

Open frmLogin in the code editor and locate the btnLogin click event code.
Tip: Double-clicking the Login button in the form designer will also bring up the event code in the code editor.
Declare and instantiate a variable of type Employee called oEmployee:
```
Dim oEmployee As Employee = New Employee()
```
Call the Login method of the oEmployee object, passing in the values of the login name and the password from the text boxes on the form:
```
oEmployee.Login(txtName.Text, txtPassword.Text)
```
Show a message box stating the user’s security level retrieved by reading the SecurityLevel property of the oEmployee object:
```
MessageBox.Show ("You have security clearence level " & oEmployee.SecurityLevel.ToString)
```
Select File > Save All
Select Build > Build Solution. Make sure there are no build errors in the Error List window. If there are, fix them, and then rebuild.
Select Debug > Start to run the project. Test the login form by entering a login name of Raja and a password of pheak. You should get a message indicating a security level of 2. Try entering your name and a password of pass. You should get a message indicating the login failed.
After testing the login procedure, close the form, which, in turn, will stop the debugger.