Ytukyg

MyProduct is the model that has HasError boolean property (with OnPropertyChanged ...) that can change.
MyProductDialogViewModel is:

class ProductDialogViewModel : Notifier

{

    public ProductDialogViewModel() { }        

    public MyProduct Product { get; set; }               

    public bool HasError

    {

        get { return Product.HasError; }

    }

}

I have assigned MyProductDialogViewModel instance to BaseContentControl.DataContext to inflate a ContentControl.
This View can be inflated with different ViewModels all having HasError property using template binding.

<ContentControl x:Name="BaseContentControl" Content="{Binding}" ... >

Then I try to extract informations directly from its DataContext.
This don't work:

<Label Content="{Binding ElementName=BaseContentControl, Path=DataContext.HasError}"/>

But this works perfectly.

<Label Content="{Binding ElementName=BaseContentControl, Path=DataContext.Product.HasError}"/>

I tought it ca be a notifiy problem in the ViewModel so I have changed to this:

class ProductDialogViewModel : Notifier

{

    public ProductDialogViewModel() { }



    public MyProduct Product { get; set; }        



    public bool HasError

    {

        get { return Product.HasError; }

        set

        {

            if (Product.HasError != value)

            {

                Product.HasError = value;

                OnPropertyChanged("HasError");

            }

        }

    }

}

but to no avail (in fact the set method is never called so it never notifies).

I don't want to directly refer to the specific Model instance cause the View can be inflated with different ViewModels.
How can I do ?

Thanks

You have to propagate the PropertyChanged event of MyProduct, i.e. subscribe to it and invoke OnPropertyChanged(nameof(HasError)) if HasError property of MyProduct being changed:

public class ProductDialogViewModel : Notifier

{

    public ProductDialogViewModel() { }



    private MyProduct _product = null;

    public MyProduct Product

    {

        get { return _product; }

        set

        {

            if (_product!=null)

            {

                _product.PropertyChanged -= Product_PropertyChanged;

            }

            _product = value;

            if (_product != null)

            {

                _product.PropertyChanged += Product_PropertyChanged;

            }

        }

    }



    private void Product_PropertyChanged(object sender, PropertyChangedEventArgs e)

    {

        if (e.PropertyName==nameof(MyProduct.HasError))

        {

            OnPropertyChanged(nameof(HasError));

        }

    }



    public bool HasError => Product.HasError;

}