Question

I need an example of linq to xml query.

I have two ListBoxes with SelectionMode set to Multiple.

My query for populating first ListBox is:

var query = doc.Root.Descendants("Articles")
                    .OrderBy(b => b.Element("Category").Value)
                    .Select(b => b.Element("Category").Value)
                    .Distinct();

and binding it with:

lbxItems.DataSource = query;
lbxItems.DataBind();

So i have all the values in first ListBox, and when i select item from that ListBox i want to populate second ListBox.

So on SelectedIndexChanged i have another query:

var query = doc.Root.Descendants("Articles")
                .Where(b => b.Element("Category").Value.Equals(lbxItems.SelectedValue))
                    .OrderBy(b => b.Element("SubCategory").Value)
                    .Select(b => b.Element("SubCategory").Value)
                    .Distinct();

That’s working if i select one item, but i need a query that is doing the same thing but from multiple selected items.

Thank you.

Answer 1

Try changing your where clause like so:

.Where(b => lbxItems.Items
    .Cast<ListItem>() // needs a cast
    .Where(i => i.Selected)
    .Select(i => i.Value)
    .Contains(b.Element("Category").Value))

The idea is to determine what items are selected and see if your category value is among those selected.