1. Fix missing event modifier on AlgorithmProgress.ProgressChanged.
2. Fix missing event modifier on AlgorithmObserverFactory<T>.Created.
3. Update documentation comments.

1. New interface IAlgorithmObserverFactory<T> and a set of APIs have been added to support algorithm observation.
2. All built-in algorithms now can be observed with the new APIs.
3. Add new interfaces INode<T> and IAlgorithmState<T> that provide abstract views of node and state information have been added for simpler algorithm observation.
4. Fix incorrect documentation comments and grammatical errors.

Including the following changes since v1.2.0-beta:

1. The interface IAlgorithmObserverFactory has been replaced with IAlgorithmObserverFactory<T> for easier use from caller's side.
2. All APIs that accept IAlgorithmObserverFactory arguments have been changed.
3. Fix grammatical errors in documentation comments.

Including the following changes:

• New interface IAlgorithmObserverFactory and a set of APIs have been added to support algorithm observation.
• All built-in algorithms now can be observed with the new APIs.
• Fix incorrect documentation comments and grammatical errors.

The h(n) (orderby clause) can now be omitted for some of the algorithms. If the h(n) (orderby clause) is not given and TFactor does not implement IComparable<TFactor> interface, only g(n) will be used to compare. For algorithms that require orderby clause, InvalidOperationException will be thrown.

Algorithms that require h(n):

• Best-first Search
• Recursive Best-first Search
• Iterative Deepening A*

Algorithms that can work without h(n):

• A* (works as Dijkstra's algorithm if h(n) is not given)

• Rename main namespace from LinqToAStar to Heuristic.Linq.
• Rename sub-namespace Core to Algorithms.
• Add native ToArray(), ToList(), Count(), LongCount(), First(), FirstOrDefault(), Last(), LastOrDefault() support.
• Improve exception message when algorithms are unable to evaluate nodes.
• Fix incorrect comparison behavior when multiple heuristic functions are applied.

Including following changes:

• Improve A* Search algorithm performance.
• Improve Best-first Search algorithm performance.
• Fix a bug where Reverse() does not work.
• Fix a bug where A* Search algorithm will not end.
• The property HeuristicSearch.RegisteredAlgorithms now will contains preset algorithms.

This is the initial release on NuGet.