Question

I don’t know if this is possible or not, but here is the code to explain the question in the title:

public class LogicClass : INotifyPropertyChanged
{
    private String _myText;
    public String MyText
    {
        get{return _myText;}
        set
        {
            _myText = value; 
            PropertyChanged(this, new PropertyChangedEventArgs("MyText"));
        }
    }
    ...
}

public partial class Window1: Window, INotifyPropertyChanged
{
    private LogicClass _logic;
    public String LogicText
    {
        get{return _logic.MyText;}
    }
    ...
}

<ContentControl Name="contentControl1" >
    <Binding ElementName="MainWindow" Path="LogicText"/>
</ContentControl>

Is there any way to make this work, without having to expose my LogicClass variable and make use of its implementation of INotifyPropertyChanged. I guess I want to know if this can bubble up, or anything other than having to have a redundant set in my UI code-behind (which is how I am doing this now)

Answer 1

Yes, you need to either handle the PropertyChanged event from _logic and then raise an equivalent PropertyChanged notification on LogicText, or you need to add a standard event on MyText, so you would have a MyTextChanged event, handle this and then raise the PropertyChanged for LogicText.

So if LogicClass if never bound to directly in the Xaml, you wouldn’t need to implement INotifyPropertyChanged on LogicClass and you would do (something like) this:

public class LogicClass
{
    private String _myText;

    public event EventHandler MyTextChanged;

    public String MyText
    {
        get{return _myText;}
        set
        {
            _myText = value; 
            var handler = MyTextChanged;
            if(handler != null){ MyTextChanged(this, EventArgs.Empty); }
        }
    }
    ...
}

public partial class Window1: Window, INotifyPropertyChanged
{
    private LogicClass _logic;

    public Window1()
    {
       _logic = ... initialised;
       _logic.MyTextChanged += (s,e) => RaisePropertyChanged("LogicText");
    }


    public String LogicText
    {
        get{return _logic.MyText;}
    }
    ...
}