Enabling LINQ for BindingListView

Question

Andrew Davies created an excellent little class on sourceforge called BindingListView which essentially allows you to bind a collection to a Data

Answer 1

Because the BindingListView<T> project uses .NET Framework v2.0 and predates LINQ, it doesn't expose an IEnumerable<T> for you to query on. Since it does implement non-generic IEnumerable and non-generic IList, you can use Enumerable.Cast<TResult> to convert the collection into a form suitable for use with LINQ. However, this approach isn't that helpful because the IEnumerable that AggregateBindingListView<T> returns is an internal data structure with type KeyValuePair<ListItemPair<T>, int>.

To upgrade this project for convenient use with LINQ, the simplest approach might be to implement IEnumerable<T> on AggregateBindingListView<T>. First add it to the declaration of the class:

public class AggregateBindingListView<T> : Component, IBindingListView, IList, IRaiseItemChangedEvents, ICancelAddNew, ITypedList, IEnumerable<T>

and then implement it at the end of the class definition:

#region IEnumerable<T> Members

IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
    for (int i = 0; i < _sourceIndices.Count; i++)
        yield return _sourceIndices[i].Key.Item.Object;

}

#endregion

and now you can use LINQ directly on a BindingListView<T> instance like this:

// Create a view of the items
itemsView = new BindingListView<Item>(feed.Items);
var descriptions = itemsView.Select(t => t.Description);

Remember to upgrade all the projects from .NET Framework v2.0 to .NET Framework 4 Client Profile and add using System.Linq; in order for this to work with your current project.

Answer 2

Ok this is what I got: Here is my extension method :

public static class BindingViewListExtensions
{
  public static void Where<T>(this BindingListView<T> list, Func<T, bool> function)
  {
    // I am not sure I like this, but we know it is a List<T>
    var lists = list.DataSource as List<T>;

    foreach (var item in lists.Where<T>(function))
    {
        Console.WriteLine("I got item {0}", item);
    }
  }

}

And then I used it like :

    List<string> source = new List<string>() { "One", "Two", "Thre" };

    BindingListView<string> binding = new BindingListView<string>(source);

    binding.Where<string>(xx => xx == "One");

I guess where in the extension method could return the found item.