Hi Yana,

I am unable to run your SDK browser (too many dependencies on things I don't have installed), but just by looking at the code of the Combo+Checkbox example, I don't think it deals with the problem I described.

My initial bug report wasn't quite right, but wasn't wrong either :)

I don't want to replace the whole collection. The problem is that unless you fire SelectAllCommand from codebehind (and that's the only way this works), whatever you added to SelectedItems will be destroyed the moment you try to interact with the control.

Let's say you have 10 items in your ItemsSource.

Add all 10 of those programatically to SelectedItems. They are visible as tokens. Everything is fine.

Open the dropdown.

Nothing is selected.

Try to select anything from the dropdown and the entire SelectedItems gets overwritten by whatever single item you clicked on.

If you don't interact with the control, SelectedItems is untouched. But if you do, it gets blown up.

So, the *only* way to make this work is as follows. Let's assume you have a list of 5 items and 2 need to be selected.

1) Add those 2 to ItemsSource

2) Fire SelectAllCommand from codebehind; the control will internally populate its internal selection list and SelectedItems

3) Add the remaining 3 items to ItemsSource

There's just no other way, CheckBox examples or not.

I have found a workaround in codebehind, but it's not very pretty in an MVVM app.

Basically, to make this work, the itemsSource for the combobox needs to be set to the selected items, then the SelectAll command should be invoked for the control to get itself together, then the non-selected tags inserted at index directly into ItemsSource.

if (_viewModel.Parameter.Tags.Count > 0)
{
    rcbTags.ItemsSource = _viewModel.Parameter.Tags;
    rcbTags.SelectAllCommand.Execute(null);
 
    for(var n = 0; n < _viewModel.TagsList.Count; n++)
    {
        if (!_viewModel.Parameter.Tags.Any(x => x.ID == _viewModel.TagsList[n].ID))
            (rcbTags.ItemsSource as List<Tag>).Insert(n, _viewModel.TagsList[n]);
    }
}