public virtual void RemoveTimeEntry(int timeEntryId)
{
var timeEntry = TimeEntries.Single(te => te.Id == timeEntryId);
if (timeEntry == null)
{
throw new EntityDeleteException("Timeentry not found in task: " + timeEntryId);
}
if (timeEntry.Invoice != null)
{
throw new EntityDeleteException("Timeentry cannot be deleted when billed: Id:" + timeEntry.Id);
}
TimeEntries.Remove(timeEntry);
}