Vb.net Property Get and set values without Private variables - vb.net

Question

Greetins,
I am programmer from some time only, I have certain doubts in fundamentals, could you please clarify on the following:
Case 1:
Public Class BillItems
Implements INotifyPropertyChanged
Public Event PropertyChanged As PropertyChangedEventHandler Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
Private Sub NotifyPropertyChanged(ByVal info As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
End Sub
Private _BillIdValue As String
Property BillId As String
Get
Return _BillIdValue
End Get
Set(ByVal value As String)
If Not _BillIdValue = value Then
_BillIdValue = value
End If
End Set
End Property
End Class
Case 2:
Public Class BillItems
Implements INotifyPropertyChanged
Public Event PropertyChanged As PropertyChangedEventHandler Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
Private Sub NotifyPropertyChanged(ByVal info As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
End Sub
Property BillId As String
Get
Return BillId
End Get
Set(ByVal value As String)
If Not BillId = value Then
BillId = value
End If
End Set
End Property
End Case
Does case 1 and case 2 yield same result, I mean is a private value necessarily in there?, can we use property itself to use its own value in its Set and get statements?
Thank you.

Answer 1

I can't imagine that Case 2 is going to run without causing a stack-overflow exception. You are essentially making an infinite loop that is going to constantly call itself.
Case 1 would be the right way to do it.
If you are using .Net 4 you could just do this (without the further Get/Set code):
Property BillId As String
This will generate the private member variable (_BillId) for you.
Edit:
You could try this to raise the event:
Property BillId As String
Get
Return _BillIdValue
End Get
Set(ByVal value As String)
If Not _BillIdValue = value Then
_BillIdValue = value
NotifyPropertyChanged("BillId")
End If
End Set
End Property

Answer 2

In this article on MSDN about Auto-Implemented Properties you can read that a property requires a standard syntax when you
Add code to the Get or Set procedure of a property, such as code to validate incoming values in the Set procedure. For example, you might want to verify that a string that represents a telephone number contains the required number of numerals before setting the property value.
Therefore, because you implement IPropertyChanged interface, you need to add code to the setter.
and write something like this.
Property BillId As String
Get
Return _BillIdValue
End Get
Set(ByVal value As String)
If Not _BillIdValue = value Then
_BillIdValue = value
NotifyPropertyChanged("BillID")
End If
End Set
End Property
The second case is clearly wrong. (Infinite loop as someone else has already said)