Exercise 7-1 Add exception handling to the simple calculator

In this exercise, youll add exception handling to the Simple Calculator form of exercise 6-1.

1. Open the SimpleCalculator project in the Assignment Exercises\Chapter 07\SimpleCalculator With Exception Handling directory.

2. Add a TryCatch statement to the btnCalculate_Click event handler that will catch any exceptions that occur when the statements in that event handler are executed. If an exception occurs, display a dialog box with the error message, the type of error, and a stack trace. Test the application by entering a nonnumeric value for one of the operands.

3. Add three additional catch blocks to the TryCatch statement that will catch an InvalidCastException, an OverflowException, and a DivideByZeroException. (If you used the ToDecimal method of the Convert class instead of the CDec function to convert the operands entered by the user to decimals, you should catch a FormatException instead of an InvalidCastException.) These catch blocks should display a dialog box with an appropriate error message.

4. Test the application again by entering a nonnumeric value for one of the operands. Then, enter 0 for the second operand as shown above to see what happens.

Here is my current Visual Basic code:

Public Class Form1 ' Calculate button click event handler Private Sub btnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click

' Reading data from text boxes Dim operand1 = Convert.ToDecimal(tbOperand1.Text) Dim operand2 = Convert.ToDecimal(tbOperand2.Text)

' Reading operator Dim operator1 = tbOperator.Text

Dim result As Decimal

' Calculating result result = calculate(operand1, operand2, operator1)

' Writing result tbResult.Text = Decimal.Round(result, 4).ToString()

End Sub

' Function that calculates the appropriate operation based on user input Private Function calculate(ByVal operand1 As Decimal, ByVal operand2 As Decimal, ByVal operator1 As String) As Decimal

Dim result As Decimal

' Executing corresponding statements Select Case operator1

' Add Case "+" result = operand1 + operand2

' Subtraction Case "-" result = operand1 - operand2

' Multiplication Case "*" result = operand1 * operand2

' Divison Case "/" result = operand1 / operand2

' Any other operator Case Else result = 0 End Select

' Returning result Return result

End Function ' Exit button click event handler Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click

' Exiting Application Application.Exit()

End Sub

Private Sub Form1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown

' If Escape key is Pressed If e.KeyCode = Keys.Escape Then btnExit_Click(sender, e) End If

' If enter key is pressed If e.KeyCode = Keys.Enter Then btnCalculate_Click(sender, e) End If

End Sub End Class