Validating Numerics

[Bananafish]

using the keypress event I can validate a text box for isdigit (0-9) isletter (A-Z)

What I would really like is to validate for a decimal value, ie
0, 4, 66.12 etc.

is there a simple way of doing this in .net?
(There is an isNumeric but that doesnt allow decimal point and does allow Hex)

Thanks for any help

[DevGrp]

Maybe you can use the substring or indexof methods to find the period. I dont think there is an easier way, but I may be wrong.

[Bananafish]

thanks for thre reply

I have written a little routine to do it - it just occured to me that ther may have been an easy way. (and being lazy - I thought Id ask here).

[ljlevend]

Another way is to create a string of allowed characters and then see if the character that corresponds to the pressed key is in the string. I don't know the exact code, but it would look something like this:

Function ChrIsAllowed

Const AllowedCharacters as String = "-.0123456789"

'This is the part that I'm not sure about, but it should be close
Return InStr(Chr(PressedKey),AllowedCharacters)

End Function

Of course you could then test to make sure that the resultant string is a number and not something like "04.4-697.-2"

[Bananafish]

Just for info, this is the function I created to validate it. As it happens I don't need to be able to enter negative values so I haven't added code for that.

I could also perhaps have an overriding class that uses a string and not a textbox, however the reason I did it with a textbox was because I will need to add code to incorporate the selstart and sellength properties...

However - for now.

To Use...

Private Sub txtAmount_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtAmount.KeyPress
 
      If Not Common.Utilities.cUtils.isValidDecimal(txtAmount, e, 3) Then
         Beep()
         e.Handled = True
      End If
End Sub

Shared Function isValidDecimal(ByVal txtBox As System.Windows.Forms.TextBox, _
           ByVal e As System.Windows.Forms.KeyPressEventArgs, _
           Optional ByVal intDecPlace As Int32 = -1) As Boolean
 
      '**************************************************
      '* Is Numeric Only (including decimal)            *
      '**************************************************
      If Not e.KeyChar = ControlChars.Back Then
         If Not e.KeyChar.IsDigit(e.KeyChar) Then
            If e.KeyChar <> "." Then
               Return False
            Else
               '***************************************
               '* Only allow one decimal point        *
               '***************************************
               If txtBox.Text.IndexOf("."c) > -1 Then
                  Return False
               End If
            End If
         Else
            '***************************************
            '* Only allow specified decimal places *
            '***************************************
            If intDecPlace > 1 Then
               Dim intX As Int32 = txtBox.Text.IndexOf("."c)
               If intX > -1 Then
                  If txtBox.Text.Length - intX > intDecPlace Then
                     Return False
                  End If
               End If
            End If
         End If
      End If
      Return True
 
   End Function