如何选择列表框中的所有项目并在ASP.NET C＃Webform中将它们串联起来？

Question

Right now I have

  String myString = listbox1.Text.ToString();

However this only returns only the 1st item, even if I hit ctrl and select all of them.

Thanks for any help

Answer 1

You are right, WebForms ListBox doesn't have the SelectedItems property. However, you can do

listBox.Items.OfType<ListItem>().Where(i => i.Selected);

That will give you the items you are looking for.

If you can't use LINQ, just do a foreach over listBox.Items, and do whatever you want when the item is Selected.

Answer 2

Using an extension method, you can do this:

public static class Extensions
{
    public static IEnumerable<ListItem> GetSelectedItems(this ListItemCollection items)
    {
        return items.OfType<ListItem>().Where(item => item.Selected);
    }
}

Usage:

var selected = listbox1.Items.GetSelectedItems();

---

Now you can take the IEnumerable<ListItem> and convert that to a string array, then finally make it into a single string separated by semicolons, like this:

// Create list to hold the text of each list item
var selectedItemsList = new List<string>();

// Create list to hold the text of each list item
var selectedItemsList = selected.Select(listItem => listItem.Text).ToList();

// Build a string separated by comma
string selectedItemsSeparatedByComma = String.Join(",",
    selectedItemsList.ToArray());