Question

I have two listviews, one for Images and one for Tags, which have a many-many relationship.

Both listviews are bound to ObservableCollection of EF objects. The Tag listview also has a checkbox column.

When I select an Image from the listview I’d like the associated Tags to be checked on the other listview. I need TwoWay binding to create and remove the relationships based on being checked or not.

How can I do this?

Answer 1

I’ve got this working as follows:

• I have extended my Tag model to have an MatchesImage boolean property
• I have bound the checkbox in my listviewitem twoway to this property
• The getter gets the CurrentImage and returns CurrentImage.Tags.Contains(this)
• When I change the checkbox in the property setter I retrieve the CurrentImage from my viewmodel (my viewmodels are global resources) and add/remove the Tag from it’s Tags collection based on value
• I will probably change CurrentImage to be accessible via a data repository, instead of the viewmodel

Something along the lines of:

public partial class Tag : INotifyPropertyChanged

  public bool MatchesImage {
    get
    {
        Image img = DataRepository.CurrentImage;
        return (img != null) ? this.Images.Contains(img) : false;
    }
    set
    {
        Image img = DataRepository.CurrentImage;
        if (img != null)
        {
            if (value)
                img.Tags.Add(this);
            else
                img.Tags.Remove(this);
            OnPropertyChanged("MatchesImage");
        }
    }
  }
}