Radscheduler for Winforms filtering and making updates for entity framework

I am trying to work on a scheduler interface that will allow a user to enter appointments.

The system is working when I apply no filter and load data through the following:

try
{
entities.Appointments.Load();
schedulerBindingDataSource1.EventProvider.DataSource = entities.Appointments.Local.ToBindingList();//filteredAppointmentsByLocation;
this.radScheduler1.DataSource = schedulerBindingDataSource1;
}

The above works and allows me to add, edit and delete without issues.

If I try to add a filter to get specific information:
var filteredAppointmentsByLocation = entities.Appointments.Local.ToBindingList().Where(x => x.LocationID.Equals(ActiveLocation));

and set this as the datasource, I cannot add new items when I do entities.SaveChanges().  I get an error saying it cannot add to a read-only or fixed-size list.  Edits are saved, deletes are not done.

Please advise