divide by zero while entering a numeric value that begins with 0

[nina_le_huynh]

basically I have a textbox

    Private Sub txt_NumberA_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txt_NumberA.TextChanged
        
        Try
            NumberA = Decimal.Parse(txt_NumberA.Text)
        Catch ex As Exception
            MsgBox("This program requires a numeric input.  Please try again. Enter .500 as 0.500.")
            Return
        End Try
        
        NumberB = 5.0
        
        NumberC = NumberB/NumberA

lbl_NumberC.Text = NumberC

    End Sub

I have no problem entering any number that does not start with a zero, however, if I want to enter 0.5 in, then as I type in '0', then I have division by zero and the program crashes.

Could you please help me to fix this? Many thanks,

Nina

[03myersd]

Try this:

    Private Sub txt_NumberA_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txt_NumberA.TextChanged
        If Val(txt_NumberA.Text) <> 0 Then
            Try
                numbera = Decimal.Parse(txt_NumberA.Text)
            Catch ex As Exception
                MsgBox("This program requires a numeric input. Please try again. Enter .500 as 0.500.")
                Return
            End Try

            numberb = 5.0

            numberc = numberb / numbera

            lbl_NumberC.Text = numberc
        End If
    End Sub

[nina_le_huynh]

03myersd,
It worked, thank you very much.
Nina

Try this:

    Private Sub txt_NumberA_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txt_NumberA.TextChanged
        If Val(txt_NumberA.Text) <> 0 Then
            Try
                numbera = Decimal.Parse(txt_NumberA.Text)
            Catch ex As Exception
                MsgBox("This program requires a numeric input. Please try again. Enter .500 as 0.500.")
                Return
            End Try

            numberb = 5.0

            numberc = numberb / numbera

            lbl_NumberC.Text = numberc
        End If
    End Sub

[dbasnett]

If the user is going to type in 53 your code displays in lbl_NumberC.Text the following:
1.0
.09

Is that what you wanted or did you just want the .09? If so you are in the wrong event handler, and also why you had the problem with 0.

[Shaggy Hiker]

I'd say you are in the wrong event handler, too. Re-doing the calculation for every character being entered means lots of extra work. LostFocus might be a better place.

However, this code will be faster. Catching an exception is a painfully slow process (though there is no cost if no exception is thrown), so using TryParse will produce better average results than dealing with an exception.

Private Sub txt_NumberA_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txt_NumberA.TextChanged
        
        if not Decimal.TryParse(txt_NumberA.Text,NumberA)
         MsgBox("This program requires a numeric input.  Please try again. Enter .500 as 0.500.")
            Return
        End if
        
        NumberB = 5.0
        
        if NumberA<>0 then
         NumberC = NumberB/NumberA
        else
         NumberC=0
        end if
 
lbl_NumberC.Text = NumberC.ToString
 
    End Sub