Q:

WPF controls, disable changes to `SelectedItem` when bound property to `ItemsSource` changes

When I use ComboBox or other controls that have ItemsSource and SelectedItem property bindings then each time upon the initial binding during runtime and also each time when the bound collection to ItemsSource changes I experience that the content of bound SelectedItem object is changed.
How can I disable this? 
For example:
I have <ComboBox MinWidth="300" ItemsSource="{Binding AvailableMasters}" SelectedItem="{Binding SelectedMaster}">
When I run the application the SelectedMaster property is assigned the first item in AvailableMasters. Also, each time the AvailableMasters collection changes (for example, by assigning a new collection to the property) the SelectedMaster is again adjusted.
The desired behavior is that SelectedItem (SelectedMaster) is only populated/changed when the end-user clicks with the mouse on that item / chooses that item from the ComboBox or other control. 

A:

Set a flag/bool property before you update the collection and use it in SelectedMaster property. Or do you need only XAML solution?

