Return false if char is repeated - vb.net

Question

I'm coding in a DataGridView, and validating if the cell has a format of numbers and comma only, the cell is for document pages,
sample format that would return true, or accept: 1,2 or 1,2,5 BUT NOT 1,,2 or 1,,,6,2
I have made a function for that, and it works fine, BUT I'm not comfortable using my code, I hope there is a better code than I have.
Please correct my code for better.
Thanks.
Private Function isCELLPageNumb(ByRef valyo As String, ByVal origMaxPage As String) As Boolean
If valyo = "0" Or valyo = "," Then
valyo = origMaxPage
Return False
End If
Dim allowedChars As String = "0123456789,"
For i As Integer = (valyo.Length - 1) To 0 Step -1
If allowedChars.IndexOf(valyo(i)) = -1 Then
valyo = origMaxPage
Return False
End If
Try
If valyo(i) = "," Then
If valyo(i + 1) = "," Then
valyo = origMaxPage
Return False
End If
End If
Catch ex As Exception
valyo = origMaxPage
Return False
End Try
''I THINK I HAVE TO SEE IF THE COMMA NEXT NUMBER IS GREATER THAN THE MAXPAGE
''If valyo(i)>origMaxPage then
''End If
Next
Return True
End Function
Edited the origMaxPage
Private Function isCELLPageNumb(ByRef valyo As String, ByVal origMaxPage As String) As Boolean
If valyo = "0" Or valyo = "," Then
valyo = origMaxPage
Return False
End If
Dim allowedChars As String = "0123456789,"
For i As Integer = (valyo.Length - 1) To 0 Step -1
''IF ALLOWED CHARACTERS NOT IN THE INDEX
If allowedChars.IndexOf(valyo(i)) = -1 Then
valyo = origMaxPage
Return False
End If
Try
''IF VALYO IS COMMA REPEATED
If valyo(i) = "," Then
If valyo(i + 1) = "," Then
valyo = origMaxPage
Return False
End If
End If
Catch ex As Exception
valyo = origMaxPage
Return False
End Try
Try
''IF VALYO GREATHER THAN THE MAXPAGE
If valyo(i) = "," Then
Dim twodigit As String = valyo(i + 1) & valyo(i + 2)
Dim numtwodigit As UInt32 = Val(twodigit)
If numtwodigit > origMaxPage Then
valyo = origMaxPage
Return False
End If
End If
Catch ex As Exception
valyo = origMaxPage
Return False
End Try
Next
Return True
End Function
The problem of the code, what if the maxpage is 12, then the user inputed 1,3,5,1111
?
The input may NOT accept negative number like: -1 or -123
Thanks

Answer 1

I assume that at some point you're going to need to get the page numbers anyways, so you should start with that:
Public Function ParsePageNumbers(value As String, maxPage As Integer) As List(Of Integer)
Dim values As New List(Of Integer)()
For Each strNumber As var In value.Split(","C)
Dim intValue As Integer
' if it wasn't an integer or it's greater than the max page, restore the original value
If Not Integer.TryParse(strNumber, intValue) OrElse intValue > maxPage Then
Return Nothing
End If
values.Add(intValue)
Next
Return values
End Function
This function will return Nothing if the pages numbers have invalid values. Then in your actual method you can just call this method and check for Nothing:
Private Function isCELLPageNumb(ByRef valyo As String, ByVal origValue As String) As Boolean
Dim maxPage As Integer = Integer.Parse(origMaxPage)
' if it's not parsible, restore the original value
If ParsePageNumbers(value, maxPage) Is Nothing Then
value = origMaxPage
Return False
End If
' it was all valid
Return True
End Function

Answer 2

Combined to MackieChan solution to parse integer, you should use first Regex
private rgxNumberWithComma As New System.Text.RegularExpressions.Regex("^([0-9]+,?)+$")
Public Function CheckInput(ByVal valyo As String, _
ByVal origMaxPage As Integer) As Boolean
Dim match = rgxNumberWithComma.Match(valyo)
If Not match.Success Then
Return False
Else
Dim numbers as new List(Of Integer) ‘will store added numbers
For Each Item In valyo.Split(","c)
Dim intValue As Integer
‘Check if number is a valid integer
‘Check if number is 0
‘Check if number has already added the number list
‘Check if number is greater that MaxPage
If Not Integer.TryParse(Item, intValue) _
OrElse intValue > origMaxPage _
OrElse intValue = 0 _
OrElse numbers.Contains(IntValue) Then
Return False
Else
‘Item is valid, continue
Numbers.Add(intValue)
End If
Next
End If
Return True
End Function
See Need a Regex for comma separated number list

Answer 3

Try it in your Datagridview EditingControlShowing Event ...
Private Sub DataGridView1_EditingControlShowing(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewEditingControlShowingEventArgs) Handles DataGridView1.EditingControlShowing
Try
If UCase(sCellName) = "PAGENUM" '------> change this with yours
AddHandler e.Control.KeyPress, AddressOf PageKeypress
End If
Catch ex As Exception
'...
End Try
End Sub
Private Sub PageKeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs)
Static sLast As String = ""
Dim k As Byte = Asc(e.KeyChar)
Dim sN As String = "0123456789,"
Dim sO As String = Chr(8) & Chr(13) & Chr(1) & Chr(3) & Chr(22)
Dim nMaxPage As Integer = 12 '-------change this with yours
If Not (sN & sO).Contains(e.KeyChar) Then
e.Handled = True
Else
Select Case e.KeyChar
Case ","
If sLast = "," Then
e.Handled = True
Else
e.Handled = False
sLast = ","
End If
Exit Sub
Case "0"
If sLast = "," Or sLast = "" Then
e.Handled = True
Exit Sub
End If
Case Chr(13) '-- avoid "," in end of text OR YOU CAN REMOVE THIS
If sLast = "," Then e.Handled = True
End Select
If sLast = "," Then sLast = ""
If Val(sLast & e.KeyChar) > nMaxPage Then
e.Handled = True
Exit Sub
End If
sLast &= IIf(sN.Contains(e.KeyChar), e.KeyChar, "")
End If
End Sub