Very Simple Calculator

'Very Simple Calculator - Documentation:
'   YouTube video tutorial at   -- http://www.youtube.com/user/bolenpresents
'   Form's screen capture is at -- http://imgur.com/m3H4SHx
'   Visual Basic .Net codes is at   -- http://pastebin.com/PcJ9nRdZ
'------------------------------------------------------------------------------------------
'           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:   Very Simple Calculator
' Author:         Joseph L. Bolen
' Date Created:   Jul 2014
'
' Description:    A very simple calculator demonstration in Visual
'                 Basic .NET to emphasis the need to document one's
'                 program.
'
'-------------------------------------------------------------------------------------------
' Modification History:
'
' Date          By      Description
' 07/02/2014    jlb1    Cosmetic fix to output. ToString("N3")
' 07/29/2014    jlb2    Data validation with ErrorProvider & Clear on Input TextChanged.
' 07/31/2014    jlb3    Data validation using the validating event. Also, form's AutoValidate
'                       property changed to EnableAllowFocusChange.
'-------------------------------------------------------------------------------------------

Option Strict On

Public Class MainForm

    ' Add first number to second number and show the sum.
    Private Sub AddButton_Click(sender As Object, e As EventArgs) _
        Handles AddButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim sum As Double

        ' Validate input - jlb3.
        If Not ValidateChildren() Then
            My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Hand)
            Exit Sub
        End If

        ' Convert text/string to a numeric data type.
        firstNumber = CDbl(FirstNumberTextBox.Text)
        secondNumber = CDbl(SecondNumberTextBox.Text)

        ' Process / Calculate sum.
        sum = firstNumber + secondNumber

        ' Convert number to string and output it to a label.
        'ResultValueLabel.Text = CStr(sum)                       ' Visual Basic
        'ResultValueLabel.Text = String.Format("{0:N3}", sum)    ' Visual Basic
        ResultValueLabel.Text = sum.ToString("N3")             ' .NET Framework - JLB1

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Subtract the second number from first number and show the difference.
    Private Sub SubtractButton_Click(sender As Object, e As EventArgs) _
        Handles SubtractButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim difference As Double

        ' Validate input - jlb3.
        If Not ValidateChildren() Then
            My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Hand)
            Exit Sub
        End If

        ' Convert text/string to a numeric data type.
        firstNumber = CDbl(FirstNumberTextBox.Text)
        secondNumber = CDbl(SecondNumberTextBox.Text)

        ' Process / Calculate difference.
        difference = firstNumber - secondNumber

        ' Convert number to string and output it to a label - jlb1.
        ResultValueLabel.Text = difference.ToString("N3")

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Multiply the first number by second number and show the product.
    Private Sub MultiplyButton_Click(sender As Object, e As EventArgs) _
        Handles MultiplyButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim product As Double

        ' Validate input - jlb3.
        If Not ValidateChildren() Then
            My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Hand)
            Exit Sub
        End If

        ' Convert text/string to a numeric data type.
        firstNumber = CDbl(FirstNumberTextBox.Text)
        secondNumber = CDbl(SecondNumberTextBox.Text)

        ' Process / Calculate product.
        product = firstNumber * secondNumber

        ' Convert number to string and output it to a label - jlb1.
        ResultValueLabel.Text = product.ToString("N3")

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Divide the first number by the second number and show the quotient.
    Private Sub DivideButton_Click(sender As Object, e As EventArgs) _
        Handles DivideButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim quotient As Double

        ' Validate input - jlb3.
        If Not ValidateChildren() Then
            My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Hand)
            Exit Sub
        End If

        ' Convert text/string to a numeric data type.
        firstNumber = CDbl(FirstNumberTextBox.Text)
        secondNumber = CDbl(SecondNumberTextBox.Text)

        ' Process / Calculate quotient.
        quotient = firstNumber / secondNumber

        ' Convert number to string and output it to a label - jlb1.
        ResultValueLabel.Text = quotient.ToString("N3")

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Clear the output controls and place cursor in first textbox.
    Private Sub ClearButton_Click(sender As Object, e As EventArgs) _
        Handles ClearButton.Click

        ' Clear output controls.
        ResultValueLabel.Text = String.Empty
        FirstNumberTextBox.Clear()
        SecondNumberTextBox.Clear()

        ' Clear ErrorProvider
        ErrorProvider1.Clear()

        ' Position cursor in first textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Clear ResultValueLabel when either first or second
    ' textbox value changes.
    Private Sub ClearResult(sender As Object, e As EventArgs) _
        Handles FirstNumberTextBox.TextChanged,
                SecondNumberTextBox.TextChanged

        ResultValueLabel.Text = String.Empty
    End Sub

    ' Validate FirstNumberTextBox input - jlb3.
    Private Sub FirstNumberTextBox_Validating(sender As Object, e As System.ComponentModel.CancelEventArgs) _
        Handles FirstNumberTextBox.Validating

        If Not IsNumeric(FirstNumberTextBox.Text) Then
            ErrorProvider1.SetError(FirstNumberTextBox, "Enter only a numeric value.")
            e.Cancel = True
            'ElseIf
        Else
            ErrorProvider1.SetError(FirstNumberTextBox, String.Empty)
        End If

    End Sub

    ' Validate SecondNumberTextBox input - jlb3.
    Private Sub SecondNumberTextBox_Validating(sender As Object, e As System.ComponentModel.CancelEventArgs) _
        Handles SecondNumberTextBox.Validating

        If Not IsNumeric(SecondNumberTextBox.Text) Then
            ErrorProvider1.SetError(SecondNumberTextBox, "Enter only a numeric value.")
            e.Cancel = True
            'ElseIf
        Else
            ErrorProvider1.SetError(SecondNumberTextBox, String.Empty)
        End If
    End Sub

    ' Allow form to close even if input errors exist - jlb3.
    Private Sub MainForm_FormClosing(sender As Object, e As FormClosingEventArgs) _
        Handles Me.FormClosing

        e.Cancel = False
    End Sub
End Class

' ======================================================================
' Comments and Pseudocode
' ======================================================================
 ' Add first number to second number and show the sum.
        'TODO:  Declare variables.
        'TODO:  Convert text/string to a numeric data type.
        'TODO:  Process / Calculate sum.
        'TODO:  Convert number to string and output it to a label.

       'ResultValueLabel.Text = CStr(sum)                       ' Visual Basic
       'ResultValueLabel.Text = String.Format("{0:N3}", sum)    ' Visual Basic
       'ResultValueLabel.Text = sum.ToString("N3")             ' .NET Framework

    ' Subtract the second number from first number and show the difference.
        'TODO:  Declare variables.
        'TODO:  Convert text/string to a numeric data type.
        'TODO:  Process / Calculate difference.
        'TODO:  Convert number to string and output it to a label.

    ' Multiply the first number by second number and show the product.
        'TODO:  Declare variables.
        'TODO:  Convert text/string to a numeric data type.
        'TODO:  Process / Calculate product.
        'TODO:  Convert number to string and output it to a label.

    ' Divide the first number by the second number and show the quotient.
        'TODO:  Declare variables.
        'TODO:  Convert text/string to a numeric data type.
        'TODO:  Process / Calculate quotient.
        'TODO:  Convert number to string and output it to a label.

    ' Clear the output controls and place cursor in first textbox.
        'TODO:  Clear output controls.
        'TODO:  Position cursor in first textbox.
' ======================================================================
' Starting Point
' ======================================================================
'------------------------------------------------------------------------------------------
'           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:   Very Simple Calculator
' Author:         Joseph L. Bolen
' Date Created:   Jul 2014
'
' Description:    A very simple calculator demonstration in Visual
'                 Basic .NET to emphasis the need to document one's
'                 program.
'
'-------------------------------------------------------------------------------------------
' Modification History:
'
' Date          By      Description
' 07/02/2014    jlb1    Cosmetic fix to output. ToString("N3")
'-------------------------------------------------------------------------------------------

Option Strict On

Public Class MainForm

    ' Add first number to second number and show the sum.
    Private Sub AddButton_Click(sender As Object, e As EventArgs) _
        Handles AddButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim sum As Double

        ' Convert text/string to a numeric data type.
        Double.TryParse(FirstNumberTextBox.Text, firstNumber)
        Double.TryParse(SecondNumberTextBox.Text, secondNumber)

        ' Process / Calculate sum.
        sum = firstNumber + secondNumber

        ' Convert number to string and output it to a label.
        'ResultValueLabel.Text = CStr(sum)                       ' Visual Basic
        'ResultValueLabel.Text = String.Format("{0:N3}", sum)    ' Visual Basic
        ResultValueLabel.Text = sum.ToString("N3")             ' .NET Framework - jlb1

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Subtract the second number from first number and show the difference.
    Private Sub SubtractButton_Click(sender As Object, e As EventArgs) _
        Handles SubtractButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim difference As Double

        ' Convert text/string to a numeric data type.
        Double.TryParse(FirstNumberTextBox.Text, firstNumber)
        Double.TryParse(SecondNumberTextBox.Text, secondNumber)

        ' Process / Calculate difference.
        difference = firstNumber - secondNumber

        ' Convert number to string and output it to a label.
        ResultValueLabel.Text = difference.ToString("N3")

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Multiply the first number by second number and show the product.
    Private Sub MultiplyButton_Click(sender As Object, e As EventArgs) _
        Handles MultiplyButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim product As Double

        ' Convert text/string to a numeric data type.
        Double.TryParse(FirstNumberTextBox.Text, firstNumber)
        Double.TryParse(SecondNumberTextBox.Text, secondNumber)

        ' Process / Calculate product.
        product = firstNumber * secondNumber

        ' Convert number to string and output it to a label.
        ResultValueLabel.Text = product.ToString("N3")

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Divide the first number by the second number and show the quotient.
    Private Sub DivideButton_Click(sender As Object, e As EventArgs) _
        Handles DivideButton.Click

        ' Declare variables.
        Dim firstNumber As Double
        Dim secondNumber As Double
        Dim quotient As Double

        ' Convert text/string to a numeric data type.
        Double.TryParse(FirstNumberTextBox.Text, firstNumber)
        Double.TryParse(SecondNumberTextBox.Text, secondNumber)

        ' Process / Calculate quotient.
        quotient = firstNumber / secondNumber

        ' Convert number to string and output it to a label.
        ResultValueLabel.Text = quotient.ToString("N3")

        ' Place cursor in first input textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub

    ' Clear the output controls and place cursor in first textbox.
    Private Sub ClearButton_Click(sender As Object, e As EventArgs) _
        Handles ClearButton.Click

        ' Clear output controls.
        ResultValueLabel.Text = String.Empty
        FirstNumberTextBox.Clear()
        SecondNumberTextBox.Clear()

        ' Position cursor in first textbox.
        FirstNumberTextBox.Focus()
        FirstNumberTextBox.SelectAll()
    End Sub
End Class

' ======================================================================
' MessageBox and ErrorProvider code.
' ======================================================================
' Convert text/string to a numeric data type.
        Double.TryParse(FirstNumberTextBox.Text, firstNumber)
        Double.TryParse(SecondNumberTextBox.Text, secondNumber)

'--------------------------------------------------------------------------
' Validate and convert text/string to a numeric data type with MessageBox.
        If Not Double.TryParse(FirstNumberTextBox.Text, firstNumber) Then
            MessageBox.Show("Enter only a numeric value.",
                            "Input Error",
                            MessageBoxButtons.OK,
                            MessageBoxIcon.Error)

            ' Place cursor in first input textbox.
            FirstNumberTextBox.Focus()
            FirstNumberTextBox.SelectAll()
            Exit Sub
        End If

        If Not Double.TryParse(SecondNumberTextBox.Text, secondNumber) Then
            MessageBox.Show("Enter only a numeric value.",
                            "Input Error",
                            MessageBoxButtons.OK,
                            MessageBoxIcon.Error)

            ' Place cursor in second input textbox.
            SecondNumberTextBox.Focus()
            SecondNumberTextBox.SelectAll()
            Exit Sub
        End If
'----------------------------------------------------------------------------

' Validate and convert text/string to a numeric data type w. ErrorProvider.
        If Not Double.TryParse(FirstNumberTextBox.Text, firstNumber) Then
            ErrorProvider1.SetError(FirstNumberTextBox, "Enter only a numeric value.")
            ' Place cursor in the first textbox and highlight the data.
            FirstNumberTextBox.Focus()
            FirstNumberTextBox.SelectAll()
            Exit Sub
        Else
            ErrorProvider1.SetError(FirstNumberTextBox, String.Empty)
        End If

        If Not Double.TryParse(SecondNumberTextBox.Text, secondNumber) Then
            ErrorProvider1.SetError(SecondNumberTextBox, "Enter only a numeric value.")

            ' Place cursor in the second textbox and highlight the data.
            SecondNumberTextBox.Focus()
            SecondNumberTextBox.SelectAll()
            Exit Sub
        Else
            ErrorProvider1.SetError(SecondNumberTextBox, String.Empty)
        End If

' ======================================================================
' Data Validation with the Validating Event
' ======================================================================

'Form at Design Time:

 me.AutoValidate =  Windows.Forms.AutoValidate.EnableAllowFocusChange


'Processing Procedure:

        If Not ValidateChildren() Then
            My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Hand)
            Exit Sub
        End If


'Validating Event for the TextBoxes:

    ' Validate FirstNumberTextBox input.
    Private Sub FirstNumberTextBox_Validating(sender As Object, e As System.ComponentModel.CancelEventArgs) _
        Handles FirstNumberTextBox.Validating

        If Not IsNumeric(FirstNumberTextBox.Text) Then
            ErrorProvider1.SetError(FirstNumberTextBox, "Enter only a numeric value.")
            e.Cancel = True
            'ElseIf
        Else
            ErrorProvider1.SetError(FirstNumberTextBox, String.Empty)
        End If

    End Sub

    ' Validate SecondNumberTextBox input.
    Private Sub SecondNumberTextBox_Validating(sender As Object, e As System.ComponentModel.CancelEventArgs) _
        Handles SecondNumberTextBox.Validating

        If Not IsNumeric(SecondNumberTextBox.Text) Then
            ErrorProvider1.SetError(SecondNumberTextBox, "Enter only a numeric value.")
            e.Cancel = True
            'ElseIf
        Else
            ErrorProvider1.SetError(SecondNumberTextBox, String.Empty)
        End If
    End Sub


'Form Closing Event:

    ' Allow form to close even if input errors exist.
    Private Sub MainForm_FormClosing(sender As Object, e As FormClosingEventArgs) _
        Handles Me.FormClosing

        e.Cancel = False
    End Sub

' ======================================================================