Invalidate CollectionViewSource

Question

Hi all,

I've defined the following view:

<CollectionViewSource x:Key="PatientsView" Source="{Binding Source={x:Static Application.Current}, Path=Patients}"/>

Where Patient is the following property:

public IEnumerable<Patient> Patients
{
 get
 {
  return from patient in Database.Patients
      orderby patient.Lastname
      select patient;
 }
}

Somewhere in my code, I change the Patients database, and I want to have the controls that display this data (using the "PatientsView") to be automatically notified. What's a proper way to do this? Can the CollectionViewSource be invalidated or something?

Answer 1

Table<T> does not support IListChanged events, you will have to do this yourself (I had to do the same earlier today).

Answer 2

How to invalidate a CollectionViewSource in code behind:

CollectionViewSource patientsView = FindResource("PatientsView") as CollectionViewSource;
patientsView.View.Refresh();

Answer 3

I think this is a bit more complex than it seems. Notifying your client application about changes in database is a non-trivial task. But your life is easier if the database is changed only from your application - this makes you able to put "refreshing logic" whenever you change the database.

Your "Patients" property seems to be present in one class (maybe a little more than one? :) ). And you probably bind some ListBox to the CollectionViewSource. So instead of calling Refresh on the CollectionViewSource you can make WPF re-call the getter. For this the class that has Patients property has to implement INotifyPropertyChanged interface.

The code would look like this:

public class TheClass : INotifyPropertyChanged
{
public IEnumerable<Patient> Patients
  {
    get
    {
            return from patient in Database.Patients
                   orderby patient.Lastname
                   select patient;
    }
  }

#region INotifyPropertyChanged members
// Generated code here
#endregion

public void PatientsUpdated()
{
  if (PropertyChanged != null)
    PropertyChanged(this, "Patients");
}
}

Now, call PatientsUpdated() on an instance of TheClass to trigger update of the binding.

P.S. Having said all that it just feels like a bad design somehow.