The way to support derived props or calculated props in prism?

[nodew]

I want to keep the tag of NavigationViewItem in my view model

private string _selectedNavTag;

public string SelectedNavTag
{
    get { return _selectedNavTag; }
    set { SetProperty(ref _selectedNavTag, value); }
}

And inside the view, I want to set the NavigationView.SelectedItem based on the tag in view model.
It's something like:

SelectedNavTag.OnChanged((newTag) => {
    SelectedItem = NavigationViewItems.where(item => Item.Tag = newTag)
})

Is it possible and how?

[brianlagunas]

You can do it in the setter of the property like this

public string SelectedNavTag
{
    get { return _selectedNavTag; }
    set 
    { 
        SetProperty(ref _selectedNavTag, value);
        **YourCode**
    }
}

In the action of the SetProperty method

public string SelectedNavTag
{
    get { return _selectedNavTag; }
    set { SetProperty(ref _selectedNavTag, value, **YourAction**); }
}

Or you can override the OnPropertyChanged method of BindableBase

[nodew]

Thanks, @brianlagunas. The main purpose here is to decouple the view model and view. I don't want the view model to keep an element reference.

[brianlagunas]

I don't see any element references anywhere in the code you provided

[nodew]

Sorry for the bad example code, there's what I want to do

ShellViewModel.cs

public ShellViewModel {
    private string _selectedNavTag;

    public string SelectedNavTag
    {
        get { return _selectedNavTag; }
        set { SetProperty(ref _selectedNavTag, value); }
    }
}

Shell.xmal.cs

public sealed partial Shell {
     public Shell () {
         ...
         // need some way to listen view model change here
     }
     
     private void handleTagChanged(string tag) {
         nav.SelectedItem = nav.MenuItems.where(item => Item.Tag = tag).FirstOrDefault();
     }
}

Shell.xaml

       <NavigationView x:Name="nav">
             ...
       </NavigationView>

[brianlagunas]

All that can be done in your VM with bindings