At the moment, the SelectedItem is not displayed (as readonly text in the entry text) if it is not present in the ItemSource.I suspect this is by design (but maybe a bug?) Background: In my list there are elements that are readonly, i.e. can correspond to the current selection, but cannot be selected by the user if a change is made.At the moment, the ItemSource has to be cleaned of the readonly elements before it is assigned to the ComboBox.A suggested solution would therefore be: Add a FilterDescriptors property, as in the RadCollectionView. This is taken into account in the selection list, but not for the display of the SelectedItem

Dirty workarround vor the moment:

private void cb_Loaded(object sender, EventArgs e)
{
    if (sender is RadComboBox radComboBox)
    {
        IReadOnlyList<IVisualTreeElement> children = radComboBox.GetVisualTreeDescendants();
        RadEntry entry = children.OfType<RadEntry>().FirstOrDefault();
        //entry.Text = DataContextViewModel.SelectedFieldOptionText;
        entry?.Bind(RadEntry.TextProperty, static (IComboBoxViewModel x) => x.SelectedOptionText, source: DataContextViewModel);
    }
}