Question

Program using visual basic.net

You will create a very simple two numbers calculator with save options; here is the specifications for the application. Create a form divided vertically in two halves with right and left panels 1- In the left panel you will create the following control, the label or the value of the control will be in "" and the type of the control will in [] a- "First Number" [textbox] b- "Second number" [texbox] c- "Result" [textbox] - read only d- "+" [push button] "-" [push button] "/" [push button] "*" [push button] f- "Save" [push button] "Display" [push button] 2- Operations The user will enter two numbers in the "First Number" and the "Second Number", then press the "+" for addition, "-" for subtraction, "*" multiplication and "/" the result will be displayed in the result [textbox], if the user clicked "[save]" then the operation can be displayed in the right panel when the user press [Display] Please note that the user can save up to 10 operations. Add "clear" [push button] on the right panel to clear the content, make sure that you trap all the errors and set the focus to the appropriate control after the error occurred - Make sure that the result contains the operations, I should see in the right panel something like this 1+1=2 1*2=2 and so on. - You must trap dived by Zero and a display a message to the user �Cannot Divide By Zero�, allow the user to renter another value

The main issue is figuring out how to limit the saved items added to the file to 10

Here's what I have so far:

Option Explicit On
Option Strict On
Option Infer Off

Public Class frmMain
    Private Sub frmMain_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub

    Dim decNum1 As Decimal
    Dim decNum2 As Decimal
    Dim decNum3 As Decimal

    Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
        ' accept input from text box 1 and 2
        Decimal.TryParse(txtNum1.Text, decNum1)
        Decimal.TryParse(txtNum2.Text, decNum2)

        ' add num 1 and 2 and display results
        decNum3 = decNum1 + decNum2
        txtNum3.Text = decNum1 & " + " & decNum2 & " = " & decNum3
    End Sub

    Private Sub btnSubtract_Click(sender As Object, e As EventArgs) Handles btnSubtract.Click
        ' accept input from text box 1 and 2
        Decimal.TryParse(txtNum1.Text, decNum1)
        Decimal.TryParse(txtNum2.Text, decNum2)

        ' subtract num 2 from num 1 and display results
        decNum3 = decNum1 - decNum2
        txtNum3.Text = decNum1 & " - " & decNum2 & " = " & decNum3
    End Sub

    Private Sub btnMultiply_Click(sender As Object, e As EventArgs) Handles btnMultiply.Click
        ' accept input from text box 1 and 2
        Decimal.TryParse(txtNum1.Text, decNum1)
        Decimal.TryParse(txtNum2.Text, decNum2)

        ' multiply num 1 and 2 and display results
        decNum3 = decNum1 * decNum2
        txtNum3.Text = decNum1 & " X " & decNum2 & " = " & decNum3
    End Sub

    Private Sub btnDivide_Click(sender As Object, e As EventArgs) Handles btnDivide.Click
        ' accept input from text box 1 and 2
        Decimal.TryParse(txtNum1.Text, decNum1)
        Decimal.TryParse(txtNum2.Text, decNum2)

        ' divide num 1 by num 2 and display results
        Try
            decNum3 = decNum1 / decNum2
        Catch ex As DivideByZeroException When decNum2 = 0
            MessageBox.Show("Cannot divide by 0. Please enter a valid number.")
            txtNum2.Focus()
        End Try
        txtNum3.Text = decNum1 & " / " & decNum2 & " = " & decNum3
    End Sub

    Private Sub input_validation(sender As Object, e As KeyPressEventArgs) Handles txtNum1.KeyPress, txtNum2.KeyPress
        ' validate input is a number 0-9
        If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso e.KeyChar <> "." AndAlso e.KeyChar <> ControlChars.Back Then
            e.Handled = True
        End If
    End Sub

    Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
        ' clears list box
        lstOperations.Items.Clear()
    End Sub

    Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
        ' writes up to 10 operations to sequential access files
        Dim outFile As IO.StreamWriter
        outFile = IO.File.AppendText(“operations.txt”)
        outFile.WriteLine(txtNum3.Text)
        outFile.Close()
    End Sub

    Private Sub btnDisplay_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click
        ' reads operations from a sequential access file and displays them in list box

        ' declare variables
        Dim inFile As IO.StreamReader
        Dim strOperation As String

        ' clears previous operations from list box
        lstOperations.Items.Clear()

        ' determine wether file exists
        If IO.File.Exists(“operations.txt”) Then
            ' open the file for input
            inFile = IO.File.OpenText(“operations.txt”)
            ' process loop instructions until end of file
            Do Until inFile.Peek = -1
                ' read operation
                strOperation = inFile.ReadLine
                ' add operation to list box
                lstOperations.Items.Add(strOperation)
            Loop
            ' close the file
            inFile.Close()
        Else
                MessageBox.Show("No savefile exists to display.")
        End If

    End Sub
End Class