Subroutine And Function Demo - Windows Form

'------------------------------------------------------------------------------------------
'           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 © 2014. All rights reserved.
'        All trademarks remain the property of their respective owners.
'-------------------------------------------------------------------------------------------
' Program Name:   Subroutine And Function Demo
' Author:         Joseph L. Bolen
' Date Created:   Aug 2014
'
' Description:    Demonstration of a Subroutine and a Function
'
'                 Documentation is at:
'                   App's screen image is at: http://imgur.com/CpfMsdU
'                   App's Visual Basic .NET code is at http://pastebin.com/FAtyqZSr
'                   Video tutorial at YouTube: http://www.youtube.com/user/bolenpresents
'
'-------------------------------------------------------------------------------------------

Option Strict On

Public Class MainForm

#Region " Class Level Variables"

    Private result As String

#End Region

#Region " Control Procedures"

    ' Update output using a subroutine.
    Private Sub SubroutineButton_Click(sender As Object, e As EventArgs) _
        Handles SubroutineButton.Click

        result = String.Empty

        AddTwoNumbers(FirstIntTextBox.Text, SecondIntTextBox.Text)

        SubroutineValueLabel.Text = result


        ''Using ByRef

        'Dim result As String = String.Empty

        'AddTwoNumbers(FirstIntTextBox.Text, SecondIntTextBox.Text, result)

        'SubroutineValueLabel.Text = result
    End Sub

    ' Update output using a function.
    Private Sub FunctionButton_Click(sender As Object, e As EventArgs) _
        Handles FunctionButton.Click

        FunctionValueLabel.Text = AddTwoNums(FirstIntTextBox.Text, SecondIntTextBox.Text)
    End Sub

    ' Clear all form input and output controls.
    Private Sub ClearButton_Click(sender As Object, e As EventArgs) _
        Handles ClearButton.Click

        ' Clear textboxes and value Labels.
        FirstIntTextBox.Clear()
        SecondIntTextBox.Clear()
        SubroutineValueLabel.Text = String.Empty
        FunctionValueLabel.Text = String.Empty

        ' Put cursor in first textbox.
        FirstIntTextBox.Focus()
    End Sub


    ' Clear Value labels if input textboxes change value.
    Private Sub TextBoxes_TextChanged(sender As Object, e As EventArgs) _
        Handles FirstIntTextBox.TextChanged,
                SecondIntTextBox.TextChanged

        SubroutineValueLabel.Text = String.Empty
        FunctionValueLabel.Text = String.Empty
    End Sub
#End Region

#Region " Subroutines and Functions"

    ' Subroutine to add two integers. Uses class level variable "result".
    Private Sub AddTwoNumbers(ByVal value1 As String, ByVal value2 As String)

        Dim num1, num2 As Integer

        If Not Integer.TryParse(value1, num1) Then
            result = "First value is not an Integer."
            Exit Sub
        End If

        If Not Integer.TryParse(value2, num2) Then
            result = "Second value is not an Integer."
            Exit Sub
        End If

        result = (num1 + num2).ToString()
    End Sub

    '' Subroutine to add two integers. Uses ByRef for returning parameter.
    'Private Sub AddTwoNumbers(ByVal value1 As String, ByVal value2 As String, ByRef value3 As String)

    '    Dim num1, num2 As Integer

    '    If Not Integer.TryParse(value1, num1) Then
    '        value3 = "First value is not an Integer."
    '        Exit Sub
    '    End If

    '    If Not Integer.TryParse(value2, num2) Then
    '        value3 = "Second value is not an Integer."
    '        Exit Sub
    '    End If

    '    value3 = (num1 + num2).ToString()
    'End Sub


    ' Function to add two integers
    Private Function AddTwoNums(ByVal value1 As String, ByVal value2 As String) As String

        Dim num1, num2 As Integer

        If Not Integer.TryParse(value1, num1) Then
            Return "First value is not an Integer."
        End If

        If Not Integer.TryParse(value2, num2) Then
            Return "Second value is not an Integer."
        End If

        Return (num1 + num2).ToString()
    End Function

#End Region

End Class