XAML - Binding ElementName between two UserControls

Question

I'm currently learning WPF and data binding got me...Any help is appreciated.

So I have two UserControls, let's say 1 and 2, inside and are simply displayed side-by-side in MainWindow.xaml. And in UserControl2 I want to bind something to an element of UserControl1. Like the code below that's failed(Obiviously):

{Binding ElementName=FolderView, Path=SelectedValue, Mode=OneWay}

where FolderView is a TreeView in UserControl1, and I want to get its property in UserControl2.

I'm still very new to the MVVM thing. I think a static ViewModel would have solved it (Rectify me if this is bad). But the SelectedValue property of a TreeView is readonly and I don't know how to bind it to a ViewModel.

Answer 1

Like you said MVVM could help.
You create a view for each of your UserControls. And you create a Viewmodel for each of them. I had the same problem at first look at these 2 they helped me alot with your problem. If you need more help just comment and I can explain some more.

https://social.msdn.microsoft.com/Forums/sqlserver/en-US/ecc7f9e9-ed16-40d9-89b9-d04040c46676/send-or-bind-parameters-from-a-usercontrol-to-another-usercontrol-in-wpf-mvvm?forum=wpf

https://softwareengineering.stackexchange.com/questions/408890/wpf-usercontrol-reuse-with-mvvm

Answer 2

Forget about all that binding. Turns out that when a TreeView 's SelectedItemChanged . The RoutedPropertyChangedEventArgs<object> 's NewValue contains the information I needed, which is the Tag property.

private void FolderView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
    MainViewModel.TVVM.TESTBOX = ((TreeViewItem)(e.NewValue)).Tag.ToString();
}

The MainViewModel.TVVM.TESTBOX is just a {get;set;} and MainViewModel.TVVM is a static (it's the only way I can think of, idk if static is good in this case) property of MainViewModel . Just gonna put all the related codes here for future reference.

TreeViewVM.cs

public class TreeViewVM : VMBase
{
    private string _testbox;
    public string TESTBOX
    {
        get { return _testbox; }
        set { _testbox = value;
        OnPropertyChange(nameof(TESTBOX));}
    }
}

MainViewModel.cs

public class MainViewModel
{
    public static TreeViewVM TVVM { get; set; }
    public MainViewModel()
    {
        TVVM = new TreeViewVM();
    }
}