Is this a better way to validate a text box for mobile number only?

Question

Is this a better way to validate a text box for mobile number only?

Validation:

• allow only numbers
• will not allow to paste string including characters
• allow copy from the box
• length is set to 10 without country code
• allow back space

Suggest some methods to help me improve my function.

Public Sub mob_validation(ByVal e As System.Windows.Forms.KeyPressEventArgs, ByVal mob As TextBox)
        If e.KeyChar = Chr(22) Then
            Dim output As String = New String((From c As Char In Clipboard.GetText.ToString Select c Where Char.IsLetter(c)).ToArray())
            If output = "" And Len(mob.Text) = 10 Then
                mob.ForeColor = Color.Green
            Else
                mob.ForeColor = Color.Red
                Clipboard.Clear()
            End If
        Else
            If Asc(e.KeyChar) < 48 Or Asc(e.KeyChar) > 57 Then
                If Asc(e.KeyChar) <> 8 Then
                    If Asc(e.KeyChar) <> 3 Then
                        e.Handled = True
                        mob.ForeColor = Color.Red
                    End If
                End If
            Else
                mob.ForeColor = Color.Green
            End If
        End If
    End Sub

Answer 1

Again, properly indent the code. The code was unreadable to the point that we broke our own rules and edited the code in question just to be able to review it.

Other than that, the biggest issue with this is all of the magic numbers. They mean absolutely nothing to Mr. Maintainer. Normally at this point, I tell people to create an Enum, but in this case, there's one built in. Use the Keys Enumeration to replace all of those hardcoded numbers.