Need some assistance with a Area Calculator in Visual Basics - vb.net

Question

I need some help with my code in a Rectangle calculator... So I made a rectangle area calculator that features Length, Width, Area, Number of Rectangles, and Smallest Rectangle... I am also creating a catch bock that handles invalid-cast extractions 2 of them... Also a A expectation class when the value of the result is greater then 1 Million... Here is my code
Public Class Form1
Dim area As Decimal
Dim numberofRectangles As Integer
Dim smallestRectangle As Decimal
Private Sub btnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click
Try
Dim length As Decimal = CDec(txtLength.Text)
Dim width As Decimal = CDec(txtWidth.Text)
Dim Area As Decimal = width * length
Dim numberofRectangles As Integer = numberofRectangles + 1
Dim smallestRectangle As Decimal = Math.Min(smallestRectangle, Area)
txtArea.Text = Area.ToString("n2")
txtNumberOfRectangles.Text = numberofRectangles.ToString
txtSmallestRectangle.Text = smallestRectangle.ToString("n2")
txtLength.Select()
Catch ex As InvalidCastException
MessageBox.Show("Please check entries for valid numeric data",
ex.GetType.ToString)
Catch ex As OverflowException
MessageBox.Show("Please check to make sure entries aren't too large.",
ex.GetType.ToString)
Catch ex As Exception
MessageBox.Show(ex.Message & vbNewLine & vbNewLine & ex.StackTrace,
ex.GetType.ToString)
If area < 1000000000 Then
Throw New FormatException("The rectangle Is too large!")
Return
End If
Finally
End Try
End Sub
For one I am having a error where my smallest rectangle is at 999,999,999,00 and For the expectation when the value of the result is greater then 1 Million I am having trouble as you can probably see from the code. Looking for some advice on my code
Edit: Fix the top part Now getting 0.00 in the smallest rectangle box
Should I being using me.compute somehwhere aswell

Answer 1

You misspelled smallestRecntangle - this is why you have needed to redeclare it - it's different to the class variable smallestRectangle. For this reason, you never set smallestRectangle to anything other than 999999999.
Also - you can use a value called Decimal.MaxValue to do the same thing as 999999999, but using the actual maximum possible decimal number. However, I would recommend instead you use Decimal? and assign to null initially. In code, have a check which "is if smallestRectangle is null, then set smallestRectangle, otherwise set it to the minimum of smallestRectangle and area".

Answer 2

Exception handling is for unexpected errors that are out of your control. We can test the user input so we don't need exception handling for that.
ex.GetType.ToString
This doesn't make sense. If you want to display the Exception message you can use and ampersand & and ex.Message. ex.ToString generally provides more information than you want a user to see.
TryParse will check if the string provided in the first parameter can be converted. It returns True or False. If True it will assign the converted string to the second parameter.
numberofRectangles += 1
is a shortcut way of writing
numberofRectangle = numberofRectangles + 1
The only line of code that could throw an exception is the area calculation so we will limit the Try block to that line.
Your main problem was using the Dim statement for numberofRectangles and smallestRectangle inside the Sub. These variables loose there value at End Sub. They only exist inside the Sub. Although Dim has the same meaning as Private for declaring Class level varaibles, Private is preferred. Dim is used for local variable in a method.
To avoid the problem of having smallest rectangle always being zero, I checked the count and set smallestRectangle to the first rectangles area. After that Math.Min takes over.
Private numberofRectangles As Integer
Private smallestRectangle As Decimal
Private Sub btnCalculate_Click(sender As Object, e As EventArgs) Handles btnCalculate.Click
Dim length As Decimal
Dim width As Decimal
If Not Decimal.TryParse(txtLength.Text, length) Then
MessageBox.Show("Please check entries for valid numeric data")
Exit Sub
End If
If Not Decimal.TryParse(txtWidth.Text, width) Then
MessageBox.Show("Please check entries for valid numeric data")
Exit Sub
End If
Dim Area As Decimal
Try
Area = width * length
Catch ex As OverflowException
MessageBox.Show("Please check to make sure entries aren't too large." &
ex.Message)
Exit Sub
Catch ex As Exception
MessageBox.Show(ex.Message)
Exit Sub
End Try
numberofRectangles += 1
If numberofRectangles < 2 Then
smallestRectangle = Area
Else
smallestRectangle = Math.Min(smallestRectangle, Area)
End If
txtArea.Text = area.ToString("n2")
txtNumberOfRectangles.Text = numberofRectangles.ToString
txtSmallestRectangle.Text = smallestRectangle.ToString("n2")
txtLength.Select()
End Sub