Bindable LINQ vs. continuous LINQ

Their are 2 problems both these packages try to solve: Lack of a CollectionChanged event and Dynamic result sets. There is one additional problem bindable solves, additional automatic event triggers.

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The First Problem both packages aim to solve is this:

Objects returned by a LINQ query do not provide CollectionChanged events.

Continuous LINQ automatically does this to all queries, with no change:

from item in theSource select item ;

Bindable LINQ does this when you add .asBindable to your query Source Object:

from item in theSource.AsBindable() select item ;

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The Second Problem both packages aim to solve is:

Result sets returned from a LINQ Query are static.

Normally when you do a LINQ Query your result set is unchanged until you do a new query. With these two packages, your result set is updated whenever the source is updated. (bad for performance, good for realtime updates)

Example

var theSource = new ContinuousCollection<Customer>();
var theResultSet = from item in theSource where item.Age > 25 select item;
//theResultSet.Count would equal 0.

Because your using Bindable or Continuous LINQ, you could modify theSource, and theResultSet would automatically include the new item.

theSource.Add(new Customer("Bob", "Barker" , 35, Gender.Male)); //Age == 35
//theResultSet.Count would now equal 1.

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The Additional Problem Bindable LINQ offers: (Quoting directly from their own page)

contactsListBox.ItemsSource = from c in customers
                              where c.Name.StartsWith(textBox1.Text)
                              select c;

Bindable LINQ will detect that the query relies on the Text property of the TextBox object, textBox1. Since the TextBox is a WPF control, Bindable LINQ knows to subscribe to the TextChanged event on the control.

The end result is that as the user types, the items in the query are re-evaluated and the changes appear on screen. No additional code is needed to handle events.

Indeed; the main issue with Continuous LINQ is the inability to use any collection that implements the generic IEnumerable and INotifyCollectionChanged. Bindable LINQ has no problem with using custom collections implementing the two interfaces.

May I draw your attention to another codeplex project? It's called Obtics and deals with the same issues (http://obtics.codeplex.com).

It addresses both the first the second and the additional problem and takes reactivity to a very deep level (has a demonstration with a LINQ based raytracer).

It claims full support for all LINQ statements an methods of the Enumerable class.

It uses yet another mechanism to create live queries:

var theResultSet = ExpressionObserver.Execute(
    () => from item in theSource where item.Age > 25 select item
).Cascade();