Databinding to individual properties of the main Dataobject - wpf

Question

This is my ViewModel Code:
vb:
Public Property Doctor() As Doctor
Get
Return _objDoctor
End Get
Set(ByVal Value As Doctor)
_objDoctor = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property AddDate() As Nullable(Of DateTime)
Get
Return _objDoctor.AddDate
End Get
Set(ByVal Value As Nullable(Of DateTime))
_objDoctor.AddDate = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property AddUserID() As String
Get
Return _objDoctor.AddUserID
End Get
Set(ByVal Value As String)
_objDoctor.AddUserID = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property ChangeDate() As Nullable(Of DateTime)
Get
Return _objDoctor.ChangeDate
End Get
Set(ByVal Value As Nullable(Of DateTime))
_objDoctor.ChangeDate = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property ChangeUserID() As String
Get
Return _objDoctor.ChangeUserID
End Get
Set(ByVal Value As String)
_objDoctor.ChangeUserID = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property CollaboratingPhysicianID() As Nullable(Of Int64)
Get
Return _objDoctor.CollaboratingPhysicianID
End Get
Set(ByVal Value As Nullable(Of Int64))
_objDoctor.CollaboratingPhysicianID = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property CredentialsID() As Int64
Get
Return _objDoctor.CredentialsID
End Get
Set(ByVal Value As Int64)
_objDoctor.CredentialsID = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property DisplayName() As String
Get
Return _objDoctor.DisplayName
End Get
Set(ByVal Value As String)
_objDoctor.DisplayName = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property DoctorSpecialtyID() As Int64
Get
Return _objDoctor.DoctorSpecialtyID
End Get
Set(ByVal Value As Int64)
_objDoctor.DoctorSpecialtyID = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property FirstName() As String
Get
Return _objDoctor.FirstName
End Get
Set(ByVal Value As String)
_objDoctor.FirstName = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property ID() As Int64
Get
Return _objDoctor.ID
End Get
Set(ByVal Value As Int64)
_objDoctor.ID = Value
OnPropertyChanged("Doctor")
End Set
End Property
Public Property LastName() As String
Get
Return _objDoctor.LastName
End Get
Set(ByVal Value As String)
_objDoctor.LastName = Value
OnPropertyChanged("LastName")
End Set
End Property
Here is on example of XAML that I could use:
<StackPanel>
<TextBox Text="{Binding LastName}" />
<TextBox Text="{Binding Doctor.LastName}" />
</StackPanel>
I would really prefer to bind to my data as the first textbox is so that I can do validation on changes. (if there is a way to do validation with the second way someone please let me know)
The problem is this:
If I load the doctor in the new constructor of the viewmodel as such:
Public Sub New()
If IsInDesignMode Then
Else
CreateEventSubscriptions()
End If
Me.Doctor = DoctorService.GetDoctor(4839)
End Sub
The Databinding works correctly the first time. But if I try to change the associated doctor with an Event, only the doctor.lastname binding works.
Private Sub onEdit(ByVal d As Doctor)
Me.Doctor = DoctorService.GetDoctor(d)
End Sub
I know I dont need to load a doctor from my service because I am actually passing the doctor...I was trying to see if there was something magical about using a service to fill the propery.
I got the code for my viewmodel properties using Karl Shifflet's XAML PowerToys. Knowing that Karl knows what he is doing I am not sure why I cant get this to work....hopefully it is something silly I am missing.

Answer 1

I believe if you change the doctor during an event, you should also call:
OnPropertyChanged("LastName")
Otherwise I don't think the binding code has any way of knowing the LastName property has been updated.