BMI Program Help

[ACM1989]

Okay, here's my code so far for a BMI program I'm making. It's almost completed but there's just or or two areas which need correcting.

At the moment, if the user doesn't enter a height or weight, or only enters a weight and not a height, an error appears called System.DivideByZeroException.

My question is, how can I have some sort of window which pops up telling the user to enter a height or weight when they click the submit button without having inputted anything, or if they've left out one field?

Public Class BMI
    Inherits System.Windows.Forms.Form
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'an integer is one or a group of characters has a value ranging from 0 to 255
        Dim number1 As Decimal 'user enters height
        Dim number2 As Integer 'user enters weight
        Dim answer As Decimal 'signals that the answer must be a decimal

        'Val returns the numbers contained in a string as a numeric value of appropriate type
        number1 = Val(MaskedTextBox1.Text) 'number 1 equals TextBox1
        number2 = Val(MaskedTextBox2.Text) 'number 2 equals TextBox2

        answer = Math.Round(number2 / (number1 * number1), 1) 'this shows what the calculation is. number2 (weight) is divided by number1 x number1 (height)

        'sets the variable "LOWBMI" and "HIGHBMI" as whole numbers
        Dim LOWBMI As Integer = 18.5
        Dim HIGHBMI As Integer = 25

        'if the answer equals less than what the LOWBMI is then display "You are underweight, your BMI is..."
        If answer < LOWBMI Then
            MsgBox("You are underweight, your BMI is " & answer)
            'if the answer equals more than what the HIGHBMI is then display "You are overweight, your BMI is..."
        ElseIf answer > HIGHBMI Then
            MsgBox("You are overweight, your BMI is " & answer)
            'or in any other case display "You are a healthy weight"
        Else
            MsgBox("You are a healthy weight, your BMI is " & answer)
        End If

    End Sub

End Class

[JugglingReferee]

The really simple method is:

Private Sub Submit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Submit.Click
    If MaskedTextBox1.Text = "" OrElse MaskedTextBox2.Text = "" Then
        MessageBox.Show("Required information is missing.", "Information Missing", MessageBoxButtons.OK, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1)
    Else
        ' process user input here
    End If
End Sub

[SJWhiteley]

why do you need a message box? You could validate the text boxes as text is entered, and enable/disable the button as appropriate.

[JugglingReferee]

Do you mean like this? Change the 'Is Valid" to suit your needs.

Private Sub MaskedTextBox1_Leave(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MaskedTextBox1.Leave
    If MaskedTextBox1.Text Is Valid AndAlso MaskedTextBox1.Text Is Valid Then
        Button1.Enabled = True
    Else
        Button1.Enabled = False
    End If
End Sub
 
Private Sub MaskedTextBox2_Leave(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MaskedTextBox2.Leave
    If MaskedTextBox1.Text Is Valid AndAlso MaskedTextBox1.Text Is Valid Then
        Button1.Enabled = True
    Else
        Button1.Enabled = False
    End If
End Sub

[SJWhiteley]

I would use the TextChanged event - I think the masked text box has that, but I never use them, so am not sure.

The TextChanged event is nice because it gives the user immediate feedback based on their actions, rather than trying to click a button which goes 'disabled' when they try to click it.

[Half]

You are giving the user too much freedom. Use 3 numeric UpDowns. This way only numebrs can be entered and since the decimal sign is "." in some countries and "," in others, you can eliminate a great deal of messy code when this problem becomes apparent.

Before the calculation you can check if the value of any of the NumUpDowns is problematic and show a message about that.

[JugglingReferee]

You are giving the user too much freedom. Use 3 numeric UpDowns. This way only numebrs can be entered and since the decimal sign is "." in some countries and "," in others, you can eliminate a great deal of messy code when this problem becomes apparent.

Before the calculation you can check if the value of any of the NumUpDowns is problematic and show a message about that.

I've always been told that numericUpDowns are the armpit of user controls.

[ACM1989]

The really simple method is:

Private Sub Submit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Submit.Click
    If MaskedTextBox1.Text = "" OrElse MaskedTextBox2.Text = "" Then
        MessageBox.Show("Required information is missing.", "Information Missing", MessageBoxButtons.OK, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1)
    Else
        ' process user input here
    End If
End Sub

This one works fine, but the problem is that although the error window appears if the user clicks the submit button without having typed in anything, but once you click 'OK' in that window, the error message appears again called "System.DivideByZeroException" and it highlights in yellow this part of the code: "answer = Math.Round(number2 / (number1 * number1), 1)".

[JugglingReferee]

This one works fine, but the problem is that although the error window appears if the user clicks the submit button without having typed in anything, but once you click 'OK' in that window, the error message appears again called "System.DivideByZeroException" and it highlights in yellow this part of the code: "answer = Math.Round(number2 / (number1 * number1), 1)".

Perhaps to change the code to also not allow entered values of zero?