Question

I have a listbox being populated from a combo box. What i need to do is string all the contents of the listbox together and then Aggregate it.

string cols = listbox1.items.Aggregate((f, s) => f.value + "," + s.value);

doesnt work.

Answer 1

Items is an ObjectCollection, so all you know for sure is that it contains objects. You can call ToString on any object:

        string[] items = listBox1.Items
            .OfType<object>()
            .Select(item => item.ToString())
            .ToArray();
        string result = string.Join(",", items);

Note that this is both more readable and more efficient than using aggregate, which causes multiple string concatenations.