WPF - how to bind to source in different page?

Could anyone answer a really frustrating newbie question please?! I've been hunting for an answer for a few days & have found answers to similar questions posed, but nothing that exactly solves my issue.

I'm trying to bind a textbox to the currently selected item in a listview (which itself is bound to an Observablecollection of objects, not sure if this matters).

The listview is in RecentEntities.xaml & the textbox is in Relationship.xaml, both of which are positioned on the Main Window from within Maincontrol.xaml. So they're in the same namespace but they're in different pages so using ElementName doesn't work as this just seems to look within the current page.

The issue I'm having is when trying to define the source of the textbox binding in Relationship.xaml, how do I reference the selected listview item in RecentEntities.xaml? I wondered about using RelativeSource, but this seems to only let you navigate up the tree to an ancestor of the current control. Because of how MainControl is set up, I would开发者_如何学编程 need to travel up to the parent of the textbox, then to a sibling of the parent then down to a child of a child of it in order to get to the listview!

I've explored (possibly not in enough depth) other options like resources, data context, including header files and have read something about Merged Resource Dictionaries but to be honest the more possibilities I explore, the more confused I'm getting about what I need to be doing.

Is this really as complicated as it seems?! Any pointers or help would be brilliant, thanks for taking the time to answer :) I haven't posted on here before, so if you need any code snippets please let me know.

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Can you create a ViewModel that both Views will use? Have the selected item in your listview bind to a property in the ViewModel and have the textbox bind to the same property. As long as both views reference the same instance of the viewmodel, it should work.

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With two XAML files you will have to use the model or viewmodel (depending on your choice of architecture) for synchronization.

For the listview you can use the SelectedValue to bind to a property, use Mode=OneWayToSource for this binding since you just want to update the property, not change the selection in the listview itself.