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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.

Victor
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2 Answers2

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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

Markus
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  • Thanks. I've checked those posts out and while they did teach me something, it's not a solution to my problem. The `SelectedValue` property of a `TreeView` is `readonly` and thus cannot bind to anything conventionally. I wanted to know how to *read* the property *from one xaml to another xaml*. But any other ways to achieve the same result are welcomed. – Victor Aug 27 '22 at 16:39
  • Here is a post that solved that for me https://stackoverflow.com/questions/1000040/data-binding-to-selecteditem-in-a-wpf-treeview – Markus Aug 27 '22 at 16:48
  • That worked with some tinkering, thank you for the answer! – Victor Aug 27 '22 at 17:15
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Forget about all that binding. Turns out that when a TreeView's SelectedItemChanged. The RoutedPropertyChangedEventArgs<object>'sNewValue 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();
    }
}
Victor
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