Enter numeric value only into textbox in visual basic - vb.net

Question

I am trying to set up a form to accept a telephone number, but i am unsure of how to validate it so it will only take numeric values with 11 digits.
So far i have it working to ensure that there is something in the textbox
'Validate data for Telephone Number
If txtTelephoneNumber.Text = "" Then
txtTelephoneNumber.Focus()
MessageBox.Show("You must enter a Telephone Number.", "Data Entry Error", MessageBoxButtons.OK, MessageBoxIcon.Information)

Answer 1

I'll imply you are using Windows Forms.
Write this as your TextBox's Key Pressed event.
Private Sub myTxtBox_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles myTxtBox.KeyPress
If txtTelephoneNumber.Text.Length > 11 Then
e.Handled= True
return
End If
If Asc(e.KeyChar) <> 8 Then
If Asc(e.KeyChar) < 48 Or Asc(e.KeyChar) > 57 Then
e.Handled = True
End If
End If
End Sub
This should (did not have time to test it) keep the user from inputing anything that is not a number. It should prevent him from inputting more than 11 numbers too.

Answer 2

In your textbox keydown event. Use the following:
If Not IsNumeric(Chr(e.KeyCode)) Then
e.SuppressKeyPress = True
End If
If you want allow other characters you would do it like so:
If Not IsNumeric(Chr(e.KeyCode)) And Not e.KeyCode = 8 And Not e.KeyCode = 46 Then
e.SuppressKeyPress = True
End If
'(8 = backspace key and 46 = Delete key)

Answer 3

You can try
If txtTelephoneNumber.Text = "" Or Not IsNumeric(txtTelephoneNumber.Text) Or txtTelephoneNumber.Text.Length <> 11 Then
txtTelephoneNumber.Focus()
MessageBox.Show("You must enter a Telephone Number.", "Data Entry Error", MessageBoxButtons.OK, MessageBoxIcon.Information)

Answer 4

Put this in your KeyPress event of the TextBox
'makes sure that only numbers and the backspace are allowed in the fields.
Dim allowedChars As String = "0123456789" & vbBack
'get a reference to the text box that fired this event
Dim tText As TextBox
tText = CType(sender, TextBox)
If allowedChars.IndexOf(e.KeyChar) = -1 Then
' Invalid Character
e.Handled = True
End If
if tText.Text.Length >= 11 then
e.Handled = True
End If

Answer 5

I use this for the keypress event
If e.KeyChar < CStr(0) Or e.KeyChar > CStr(9) Then e.Handled = True
Actually that looks different to what i remember using, but it works. Though you'll need to allow backspace too.
Or i guess even shorter would be
If Not IsNumeric(e.KeyChar) Then e.Handled = True
also keypress event.
You can set the maximum length of a textbox using MaxLength

Answer 6

set max length to 12 put this in keypress of text1 and it will format it with dashes and only numbers
If Len(Text1.Text) = 3 Or Len(Text1.Text) = 7 Then
Text1.Text = Text1.Text & "-"
Text1.SelStart = Len(Text1.Text)
End If
If KeyAscii <> 127 And KeyAscii <> 8 And KeyAscii <> 13 Then
If IsNumeric(Chr(KeyAscii)) = False Then
KeyAscii = 0
End If
ElseIf KeyAscii = 8 Then
If Right(Text1.Text, 1) = "-" Then
Text1.Text = Left(Text1.Text, Len(Text1.Text) - 1)
Text1.SelStart = Len(Text1.Text)
End If
End If
if you only want numeric text box use the following in the keypress
If KeyAscii <> 127 And KeyAscii <> 8 And KeyAscii <> 13 Then
If IsNumeric(Chr(KeyAscii)) = False Then
KeyAscii = 0
End If
End If

Answer 7

You can use the lostfocus event and in this event you can put something like this:
if not isnumeric(textbox1.text) then
textbox1.gotfocus 'this part is to validate only numbers in the texbox and not let
' him go from the texbox
endif
and you should define the maxlength for the textbox in just 11 characters