Could not find an implementation of the query pattern Error

Question

Given

   var selectedItems = listBoxControl1.SelectedItems;
   var selectedItemsList = (from i in selectedItems
                             select i).ToList();

I receive Error

Could not find an implementation of the query pattern for source type 'DevExpress.XtraEditors.BaseListBoxControl.SelectedItemCollection'. 'Select' not found. Consider explicitly specifying the type of the range variable 'i'.

using system.LINQ Done

I can use foreach so it must implement IEnumerable. I prefer to use LINQ over foreach to gather each string, if possible.

I want to take the ToString() values for each SelectedItem in the list box control and stick them in a List<string>. How can I do it?

Answer 1

For LINQ to work, you need an IEnumerable<T>, straight IEnumerable isn't enough. Try:

var selectedItems = listboxControl1.SelectedItems.Cast<T> //where T is the actual type of the item

Answer 2

I can use foreach so it must implement IEnumerable.

That's not actually true, but it's irrelevant here. It does implement IEnumerable, but not IEnumerable<T> which is what LINQ works over.

What's actually in the list? If it's already strings, you could use:

var selectedItemsList = selectedItems.Cast<string>().ToList();

Or if it's "any objects" and you want to call ToString you can use:

var selectedItemsList = selectedItems.Cast<object>()
                                     .Select(x => x.ToString())
                                     .ToList();

Note that the call to Cast is why the error message suggested using an explicitly typed range variable - a query expression starting with from Foo foo in bar will be converted to bar.Cast<Foo>()...