Student Class Demo

'------------------------------------------------------------------------------------------
'           Notice of My Copyright and Intellectual Property Rights
'
' Any intellectual property contained within the program by Joseph L. Bolen remains the
' intellectual property of the Joseph L. Bolen. This means that no person may distribute,
' publish or provide such intellectual property to any other person or entity for any
' reason, commercial or otherwise, without the express written permission of Joseph L. Bolen.
'
'                 Copyright © 2016. All rights reserved.
'        All trademarks remain the property of their respective owners.
'-------------------------------------------------------------------------------------------
' Program Name:   Student Class Demo
'
' Author:         Joseph L. Bolen
' Date Created:   04 MAR 2016
'
' Description:    Demonstrate the the basic concepts of a user defined class.

'
'                 Documentation is at:
'                   App's screen image is at: http://imgur.com/d90zTp8 and
'                                               http://imgur.com/FnCCAvr
'                   App's Visual Basic .NET code is at http://pastebin.com/nr6Qw8bD
'                   Video tutorial at YouTube: http://www.youtube.com/user/bolenpresents
'-------------------------------------------------------------------------------------------

Option Strict On

Imports System.Text                         ' For StringBuilder class.

Public Class StudentForm

    ' Class level (or instanciated) variables declared.
    Private studentCount As Integer = 0     ' Incremental counter.
    Private students(4) As Student          ' Simple array of student datatype.
    'Private students As New List(Of Student) ' List(Of T)

    ' Add new Student to students array.
    Private Sub AddStudentButton_Click(sender As Object, e As EventArgs) _
        Handles AddStudentButton.Click

        'Instantiate a New student And assign values to its properties.
        Try
            Dim addStudent As New Student()
            addStudent.StudentId = studentCount + 1     ' Offset by one.
            addStudent.FirstName = FirstNameTextBox.Text
            addStudent.LastName = LastNameTextBox.Text

            ' Add student to the array.
            students(studentCount) = addStudent

            studentCount += 1   ' Increment counter
            DisplayStudentsButton.Enabled = True
        Catch ex As Exception
            MessageBox.Show(ex.Message, Me.Text,
                                MessageBoxButtons.OK, MessageBoxIcon.Error)
            FirstNameTextBox.Focus()
            Exit Sub
        End Try

        ' If no more room in array, disable add button.
        If studentCount > students.GetUpperBound(0) Then
            AddStudentButton.Enabled = False
        End If

        ResetTextboxes(

        '' Using a List(Of T)
        'Try
        '    Dim addStudent As New Student With {
        '        .StudentId = studentCount + 1,
        '        .FirstName = FirstNameTextBox.Text,
        '        .LastName = LastNameTextBox.Text}

        '   Add Student to List.
        '    students.Add(addStudent)

        '    studentCount += 1   ' Increment counter
        '    DisplayStudentsButton.Enabled = True
        'Catch ex As Exception
        '    MessageBox.Show(ex.Message, Me.Text,
        '                    MessageBoxButtons.OK, MessageBoxIcon.Error)
        '    FirstNameTextBox.Focus()
        '    Exit Sub
        'End Try

        'ResetTextboxes()
    End Sub

    ' Using the StringBuilder class, output summary of students.
    Private Sub DisplayStudentsButton_Click(sender As Object, e As EventArgs) _
        Handles DisplayStudentsButton.Click

        Dim output As New StringBuilder("Student Listing:" & vbNewLine & vbNewLine)

        For idx As Integer = 0 To studentCount - 1
            output.AppendLine(students(idx).ToString)
        Next

        '' Using a List(Of T)
        'For Each student In students
        '    output.AppendLine(student.ToString)
        'Next

        MessageBox.Show(output.ToString, Me.Text)
        FirstNameTextBox.Focus()
    End Sub

    Private Sub ClearButton_Click(sender As Object, e As EventArgs) _
        Handles ClearButton.Click

        ResetTextboxes()
    End Sub

    ' Clear Textboxes on form and set focus to first input control.
    Private Sub ResetTextboxes()

        FirstNameTextBox.Clear()
        LastNameTextBox.Clear()
        FirstNameTextBox.Focus()
    End Sub

End Class

'===============================================================================================
Public Class Student

    '' Auto-implemented properties
    'Public Property StudentId As Integer
    'Public Property FirstName As String
    'Public Property LastName As String

    Private studentIdValue As Integer
    Public Property StudentId() As Integer
        Get
            Return studentIdValue
        End Get
        Set(ByVal value As Integer)
            If value < 1 Then
                Throw New ArgumentOutOfRangeException("Student Id must be a positive whole number.")
            End If
            studentIdValue = value
        End Set
    End Property

    Private firstNameValue As String
    Public Property FirstName() As String
        Get
            Return firstNameValue
        End Get
        Set(ByVal value As String)
            If String.IsNullOrWhiteSpace(value) Then
                Throw New ArgumentNullException("First Name must have a value.")
            End If
            firstNameValue = value
        End Set
    End Property

    Private lastNameValue As String
    Public Property LastName() As String
        Get
            Return lastNameValue
        End Get
        Set(ByVal value As String)
            If String.IsNullOrWhiteSpace(value) Then
                Throw New ArgumentNullException("Last Name must have a value.")
            End If
            lastNameValue = value
        End Set
    End Property

    ' Default Constructor
    Public Sub New()
        MyBase.New
    End Sub

    ' Constructor overload
    Public Sub New(ByVal id As Integer)
        StudentId = id
    End Sub

    ' Constructor overload
    Public Sub New(ByVal id As Integer, ByVal fName As String, ByVal lName As String)
        StudentId = id
        FirstName = fName
        LastName = lName
    End Sub

    Public Overrides Function ToString() As String
        Return String.Format("Student ID: {0:D3} is {1} {2}", StudentId, FirstName, LastName)
    End Function
End Class