Hmm, my column is bound to a Dictionary<int, string> so if I do like this:
var sourceCollection = (IEnumerable<KeyValuePair<
e.ItemsSource = sourceCollection.Select(item => item.Key).Distinct();
The compiler complains, saying that there is no Select method on a IEnumerable<KeyValuePair<int, string>.
I tried to just set e.ItemsSource = sourceCollection since my collection already contains distinct values, but then it will display both Key and Value in the filter like this: