C# Converting ListBox to String then Aggregate

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 + "开发者_Python百科," + s.value);

doesnt work.

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.

pretty old thread, but here's my solution if anybody need it still

string cols = string.Join(",", listBox1.Items.Cast<String>());

Supposing that you have strings in the listbox, try this:

string cols =
    String.Join(",", listbox1.Items
        .OfType<Object>()
        .Select(i => i.ToString())
        .ToArray());

Generally String.Join is used to join a string. This is faster than using a StringBuilder as the size of the new string is already known and it doesn't have to copy everything twice.

string cols = listBox1.Items.Cast<string>().Aggregate((f, s) => f + "," + s);

I think you need to explicitly do ToString()

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