Textbox Validation question

Hello guys, I wrote this code to validate a textbox... What I want is that the textbox only receive value with 0 or greater or null... The code I wrote below only work with value 0 or greater but it wouldnt' work when I leave the textbox null. Please advise what to do. Thank you.


Private Function isValidPrice2(ByVal Price2 As String) As Boolean
Dim Result As Boolean = False
If IsNumeric(Price2) Then
If Price2 > 0.0 Or Price2 = "null" Then
If CType(Price2, Double) = Price2 Then
Result = True
End If
End If
End If
Return Result
End Function

hi
try this

Private Function isValidPrice2(ByVal Price2 As String) As Boolean
Dim Result As Boolean = False
If IsNumeric(Price2) Then
If Price2 > 0.0 Or Price2 = vbnullstring Then
If CType(Price2, Double) = Price2 Then
Result = True
End If
End If
End If
Return Result
End Function

Thank you for replying... I tried that and still didnt' work... By the way, I am using Visual Basic.net

Please advise what I need to do.. Thank You

Try :

VB Code:

Private Function isValidPrice2(ByVal Price2 As String) As Boolean
        Dim Result As Boolean = False
        If IsNumeric(Price2) Then
            If Price2 > 0.0 Or Price2 = "" Then
                If CType(Price2, Double) = Price2 Then
                    Result = True
                End If
            End If
        End If
        Return Result
    End Function

It doesnt' work either.. :)... is there something wrong w/ my code?.. thanks

What do you mean it doesn't work ?? I can't see anything wrong . I did test it and it returns false I think when 'Price2' is 0 or null .

thanks for replying, Pirate.... First, please look at my code below and I'll explain to you why it didnt' work.....


-------------------------Form Class--------------------------------------------
Private Sub btTotal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btTotal.Click
Dim Order As New clsOrder()
.....
.....
If Not isValidPrice2(txtPrice2.Text) Then
Msg = "Price 2 is not valid." + vbCrLf
End If

If Msg <> "" Then
MsgBox(Msg, , "Invalid Data")

Else
txtTotal2.Text = Order.CalcTotal2(txtPrice2.Text, numQty2.Text)

End If
End Sub



Private Function isValidPrice2(ByVal Price2 As String) As Boolean
Dim Result As Boolean = False
If IsNumeric(Price2) Then
If Price2 > 0.0 Or Price2 = "" Then
If CType(Price2, Double) = Price2 Then
Result = True
End If
End If
End If
Return Result
End Function


-------------------clsOrder Class--------------------------------------------
Public Class clsOrder

Public Function CalcTotal2(ByVal Price2 As Double, ByVal Qty2 As Integer) As Double
Return Price2 * Qty2
End Function

End Class
---------------------------------------------------------------------------------


The way I set up is that I have a "Price2" textfield... I did the validation code above to have the textfield accept only the value that greater than 0... A "Price2 is not valid" messagebox will pop up if there is negative number in the "Price2" textfield...

Now when I tried your code above, it still gives me "Price2 is not valid" message box even if textfield is 0 or null... I know your code is right but somehow the message box still pop up....

Can you take a quick look at my clsOrder class or the way I arrange the code in the form class is right..... I know there's something wrong w/ the way I arrange the code but I couldnt' figure out the problem... Thanks a lot for helping...

can you not do something like this :

VB Code:

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If e.KeyChar.IsNumber(e.KeyChar) Or e.KeyChar = "." Or e.KeyChar = Chr(Keys.Back) Or e.KeyChar = Chr(Keys.Delete) Then
            e.Handled = False '/// only allow numerics , a . and the Back / Delete keys.
        Else
            e.Handled = True '/// dont allow any other keys.
        End If
    End Sub
 
    Private Sub TextBox1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TextBox1.MouseUp
        If Not IsNumeric(sender.text) Or sender.text = "." Then
            sender.text = "" '/// incase stuff gets pasted in.
        End If
    End Sub

yeah.. that's a good idea... thanks a lot..

thanks pirate and dynamic sysop for helping out....

txtBox.Text.Length >= 0 in the beggining of the if maybe :rolleyes: ?

I've tried your code and it's working :confused:. It shows the msgbox "Price 2 is not..." when the value of assigned textbox is 0 , null or negative .