Question

I’ve a ListBox in my winforms app. I want it to have as DataSource the keys of a dictionary so I do as follows:

IDictionary<Entity1, Entity2> myEntities = new Dictionary<Entity1, Entity2>();
myListBox.DataSource = myEntities.Keys;

So I’m getting at the second line the following error:

Complex databinding accepts as a datasource either in Ilist or IListSource

• I’ve tried two things that wont do:

  myListBox.DataSource = (IList<Entity1>)myEntities.Keys;

throws InvalidCastException exception:

Can’t convert an object of type ‘KeyCollection[Entity1,Entity2]’ to type ‘System.Collections.Generic.IList`1[Entity1]’.

• And And I’ve also tried:

  myListBox.DataSource = myEntities.Keys.ToList<Entity1>();

but with that way I lose the binding, when I modify myEntities, myListBox.DataSource does not change.

Note: The excepton messages are translated by me so they may not be exactly as I wrote.

Any way to do do this?

Thanks!

Answer 1

  myListBox.DataSource = (from keys in myEntities.Keys
                         select keys)
                         .ToList();

Third time a charm…

Okay,

I believe you will have to inherit the Dictionary and override the .Add method to trigger an event. On the event, you will need to re-query the Dictionary keys. According to resources I’ve found (including: How to Bind…) the Dictionary does not throw events when it’s contents change.