Question

I have a Dictionary that is declared thusly:

Dictionary myDictionary<string, List<FCPort>> = new Dictionary<string, List<FCPort>>();

the key is a string representing a switch name. The value is a list of port objects for that switch. I am trying to add the items in the Dictionary to a ListView with this code:

foreach (KeyValuePair<string, List<FCPort>> portpair in results)
        {             
            ListViewItem item1 = new ListViewItem(portpair.Key);
            foreach (FCPort port in portpair.Value)
            {
                item1.SubItems.Add(port.FCIDList[0]);
                item1.SubItems.Add(port.WWPNList[0]);
                item1.SubItems.Add(port.TextSerializePortName());
                this.ResultsListView.Items.Add(item1);

            }
        }

However, I get a run-time error basically saying that I have a duplicate item in the list. That makes sense. I am attempting to group by the dictinoary key (the switch name). Is there a way to somehow group the items in the listview, or dynamically add Listviews to the GroupBox on the fly? Basically add a new ListView for each key in the Dictionary? I am still learning C# and forms are still new.

Answer 1

you could use LINQ lookup to group by your key selector.
and extend your portpair to enumerable when add to into listview subitems

This is the code snippet I did sometimes hopefully could help you.

Dictionary<String, Country> dict = new Dictionary<string, Country>();
dict.Add("Toronto", Country.Canada);
dict.Add("New York", Country.US);
dict.Add("Vancover", Country.Canada);
dict.Add("Seattle", Country.US);
dict.Add("Fredericton", Country.Canada);

Lookup<Country,String> lookup = (Lookup<Country,String>) dict.ToLookup(pair =>pair.Value, pair => pair.Key);

 foreach (var countryGroup in lookup)
 {
    item = new ListViewItem(countryGroup.Key.ToString());
    item.SubItems.Add(string.Format("{0}", string.Join(",", countryGroup.Select(s => "@" + s))));
    lv.Items.Add(item);
    item = null;
 }