'______________________________________________________________________

'                                        CLASS INHERITANCE
'
'                                      Ron Kessler & Company
'                                  Created 8/6/06 for C# 2005

'______________________________________________________________________

'The program demonstrates:
'   1. Using muliple custom classes
'   2. Form inheritance
'   3. How to add XML documentation
'   4. How to add Windows Help to your application


'This is the program we did in class. We create two classes: Person and Teacher
'Person has two properties and one method. It calculates the age of the person.

'We create a instructor class that inherits from the person class and we add the property of subject taught.

'When the program runs, it lets us enter the name of our myEmployee. If the person is a teacher it asks for the
' subject area they teach.

'It then computes the person's age. If a teacher, it also prints out what area they teach in a label.


'NOTES:

'Updated 8/6/06

'   shows how to use String.Concat to concatenate up to 4 strings in one call
'   added checkbox for instructor status
'   also uses the instructor class properties to fill  the labels. This proves the instructor class does inherit
'   the properties of the person class (name).
'IT SHOWS HOW TO USE XML DOCUMENTATION FOR YOUR CLASSES 

Public Class frmMain

    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click

        Dim myEmployee As New Person      'new object called myEmployee based on the Person class I created
        Dim myTeacher As New Instructor
        Dim DOB As Date
        Dim Age As Integer = 0

        '---now set the properties of my class
        myTeacher.FirstName = txtFirst.Text.ToUpper      'all caps
        myTeacher.LastName = txtLast.Text.ToUpper

        '---get the date of birth from the datepicker
        DOB = DatePicker.Value.Date

        '---calculate the person's age using my age method of the myEmployee object
        Age = myEmployee.Age(DOB)


        lblAge.Text = myTeacher.FirstName & " " & myTeacher.LastName & " is " & Age & " years old. "

        '---or use new string concatenation You can connect up to four strings in one call
        'lblAge.Text = String.Concat(myEmployee.FirstName, " ", myEmployee.LastName)

        If chkTeacher.Checked Then
            myTeacher.SubjectArea = InputBox("What class do you teach?")
            lblAge.Text &= myTeacher.FirstName & " teaches " & myTeacher.SubjectArea
        End If



    End Sub

   
    Private Sub btnHelp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnHelp.Click
        System.Diagnostics.Process.Start("class inheritance1.chm")
    End Sub

    Private Sub btnEnd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnd.Click
        Me.Close()
    End Sub
End Class


'__________________________________________________________

'                                           Person Class
'                                Created 8/6/06 for C# 2005
'__________________________________________________________

'This class has two properties and one method (Age).

Public Class Person
    '---module-level properties variables
    Private first As String
    Private last As String

    ''' <summary>
    ''' Sets the value for the First Name
    ''' </summary>

  
    Public Property FirstName() As String
        Get
            Return first
        End Get
        Set(ByVal Value As String)
            first = Value
        End Set
    End Property

    ''' <summary>
    ''' Sets the value for the First Name
    ''' </summary>
    ''' 

    Public Property LastName() As String
        Get
            Return last
        End Get
        Set(ByVal Value As String)
            last = Value
        End Set
    End Property


    ''' <summary>
    ''' Computes the persons age from the DOB passed in the Age method
    ''' </summary>
    Public Function Age(ByVal DOB As Date) As Integer

        Return CInt(Now.Subtract(DOB).Days / 365)

    End Function
End Class




'__________________________________________________________

'                                           Instructor Class
'                                Created 8/6/06 for C# 2005
'__________________________________________________________

'This class has one property.

Public Class Instructor
    Inherits Person


    Private mySubjectArea As String

    ''' <summary>
    ''' Sets the value for the Subject area the instructor teaches.
    ''' </summary>

    Public Property SubjectArea() As String
        Get
            Return mySubjectArea
        End Get
        Set(ByVal Value As String)
            mySubjectArea = Value
        End Set
    End Property
End Class