How to save the IsExpanded state in group headers of a listview

Question

I have quite a tricky problem:

I am using a ListView control with the ItemsSource set to a CollectionViewSource including a PropertyGroupDescription to group the Lis

Answer 1

You could create a new class with a Dictionary (say, ObjectType as a key to bool values), and give it an indexer:

    Dictionary expandStates = new Dictionary();

    public bool this[ObjectType key]
    {
        get
        {
            if (!expandStates.ContainsKey(key)) return false;
            return expandStates[key];
        }
        set
        {
            expandStates[key] = value;
        }
    }

Then, instantiate it in a ResourceDictionary somewhere and bind the IsExpanded to it like this:

That might well do it: a nice way of getting WPF to call your code and pass a parameter just when you need it. (That WPF lets you put subexpressions in indexers in a binding path was news to me - good though isn't it!)