New Post: CheckComboBox selectedItems

A user wrote :
I'm getting a "The property "SelectedItems" does not have an accessible setter." error from the following XAML:

"
<xctk:CheckComboBox x:Name="UserGroupsCheckedComboBox" Grid.Row="1" Grid.Column="0"
ItemsSource="{Binding UserGroups}"
SelectedItems="{Binding SelectedUserGroups, Mode=OneWayToSource}"
SelectedItemsOverride="{Binding SelectedUserGroupsOverride}"
DisplayMemberPath="Name"
ValueMemberPath="ID"
Command="{Binding OnUserGroupsChangedCommand}"
Width="200"
HorizontalAlignment="Left"
VerticalAlignment="Center"

</xctk:CheckComboBox>
"