Validation Class(dll) - vb.net

Question

İ m tring to do a validation dll for may textbox. my dll's codes like this
Public Class validatedll
Function onlynumbers(ByVal r As String)
Dim list As String, character As String
Dim i As Integer
list = "1234567890"
i = 1
If r <> "" Then
cntinue:
If i > 10 Then
MsgBox("invalid character. Last character will be delete !")
r = Mid(r, 1, Len(r) - 1)
Return r
Exit Function
End If
character = Mid(list, i, 1)
If Microsoft.VisualBasic.Right(r, 1) = character Then Exit Function
i = i + 1
GoTo cntinue
Else
Exit Function
End If
End Function
End Class
And i m useing this dll in my project like this
Imports ModifiedTextbox
Public Class Form1
Public validate As New validatedll
Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
' TextBox1.Text = validate.onlynumbers(TextBox1.Text)
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
TextBox1.Text = validate.onlynumbers(TextBox1.Text)
End Sub
End Class
My problem is, if i use this dll in TextBox1_TextChanged event, Textbox1's text showing to me nothing because dll is not returning numbers. İf i use this code with button, code is working and deleting last character if a letter.
How can i use this dll in textchanged event? pls help to me.
My best regards

Answer 1

The main reason your weren't getting a return is whenever your loop found the right character it exited.
A few things:
A function should always have an As clause to specify the return type. You may remember the return today what about a year from now?
Never use GoTo. VB.net has several functional loops that will do pretty whatever you like.
Assuming that you want to extend this to support other validations you might want to consider another approach:
Public Class validatedll
Sub onlynumbers(tb As TextBox)
While Not tb.Text = "" AndAlso Not Double.TryParse(tb.Text, vbNull)
tb.Text = tb.Text.Remove(tb.Text.Length - 1)
tb.SelectionStart = tb.Text.Length
End While
End Sub
End Class
I made it a sub that gets passed a reference to the textbox. This keeps the mechanism of your validation more compartmentalized. This will also make it easier if you decide to extend this class to be a custom control.
This tests if the string is a number, and keeps subtracting characters until it's empty or is a number. This will work for on the fly validation or on exit validation.

Answer 2

i resolve my problem. Maybe somebody needs that. You can add which chars to wanna allow with orelse;
Function onlynumbers(ByVal chars As String, ByVal exclmtn As Boolean, Optional title As String = "Title what you want")
If chars = "" Then Exit Function
If _
Microsoft.VisualBasic.Right(chars, 1) = "1" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "2" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "3" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "4" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "5" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "6" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "7" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "8" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "9" OrElse _
Microsoft.VisualBasic.Right(chars, 1) = "0" Then
Return chars
Exit Function
Else
If exclmtn = False Then
chars = Mid(chars, 1, Len(chars) - 1)
Return chars
Exit Function
End If
If exclmtn = True Then
MsgBox("invalid. last char ll delete !", , title)
chars = Mid(chars, 1, Len(chars) - 1)
Return chars
Exit Function
End If
End If
End Function