Question

I am trying to make a master-details form, with the master records bound to one binding source, and the details datagridview bound to a second binding source

It works pretty well, only the childBindingSource.SupportSorting property is false.
masterBindingSource.SupportsSorting is true. Is there a way I can get the childBindingSource to support sorting – given that it is based on another binding source that does support sorting?

masterBindingSource.DataSource = GetBindingSource()   // .SupportsSorting = true
childBindingSource.DataSource = masterBindingSource   // .SupportsSorting = false
childBinding.DataMember = ChildItems

private BindingSource GetBindingSource()
{
   DbSet<ContactEvent> dset = Db.ContactEvents;
   IOrderedQueryable<ContactEvent> qry = dset.Where(p => p.Id > 0).OrderBy(x => x.Id);
   qry.Load();

   BindingList<ContactEvent> bindinglist = dset.Local.ToBindingList();
   var bindingSource = new BindingSource();
   bindingSource.DataSource = bindinglist;
   return bindingSource;
}

Answer 1

With some help we got this working using
this link at codeplex

I had to change my class to use the SortableBindingList instead of BindingList.
It was interesting to me that BindingList alone was good enough for a grid at the master level – but not for a grid containing details.