A
The Usercontrols are some elements to be part of your Window, then the Window can be the suitable connector between your UserControls. you can approach this scenario like this:
WindowAUserControlPersonList
- Include
SelectedPersion Dependency Property. SelectedPerson type is a model class or viewmodel class
UserControlPerson
Now, inside WindowA.xaml:
<StackPanel>
<userControls:UserControlPersonList x:Name="PersonListControl"/>
<userControls:UserControlPerson DataContext="{Binding ElementName=PersonListControl, Path=SelectedPerson}"/>
</StackPanel>
The result can be something like this (a master-detail view):
You need fill SelectedPerson dependency property of UserControlPersonList when you select a person. To perform this you can use Command and change SelectedPerson property in PersonListViewModel and bind SelectedPerson dependency property in UserControlPersonList to it OR do this in your UserControlPersonList level like this answer.
B
But if you want some global changed in your UserControls in different Windows you can hold the PersonListViewModel in a static property that is accessible in all of your Windows and Usercontrols of your program then create an event in it named SelectedPersionChanged. Now in your UserControls you can subscribe an EventHandler to SelectedPersionChanged and change your DataContext.
But you MUST unsubscribe your EventHandler from SelectedPersionChanged when you did not need to that UserControl anymore to prevent memory leaks.
