Limitations

There are a few things that are beyond the scope of my work:

• I cannot provide Generic Variance.
• I cannot extend reflection (I recommend to use Mono.Cecil)
• I cannot add some methods such as String.Join(string, IEnumerator<string>), I'll provide helper methods instead. Whenever possible this helper methods are going to extension methods to minimize the changes needed in code. For a list see below.
• I cannot improve the Garbage Collector. Try using Mono as a back-end.
• I will not include backports of Reactive Extensions or any other code not in the BCL, but I may provide similar functionality.
• I have no intention to backport GUI libraries.
• I cannot modify EventHandler<T> to remove the generic constraint that's present in .NET prior .NET 4.5. For workaround see below.
• I cannot modify OperationCanceledException to add support to CancellationToken. For workaround see below.
• I cannot modify HashSet<T> on .NET 3.5 to allow casting to ISet<T>
• In the type IGrouping<TKey, TElement> TKey is covariant from .NET 4.0 onward, I cannot make it covariant in .NET 3.5.

These features are not planned to be added or improved:

• Environment.SpecialFolder
• Environment.Is64BitOperatingSystem
• ServiceInstaller.DelayedAutoStart

The following are the notable methods that has been added to existing types:

• Comparer<T>.Create was added in .NET 4.5, use ComparerExtensions.ToComparer instead.
• Enum.HasFlag was added in .NET 4.0, use EnumHelper.HasFlag instead.
• Stream.CopyTo was added in .NET 4.0, use StreamExtensions.CopyTo instead.
• String.IsNullOrWhiteSpace was added in .NET 4.0, use StringHelper.IsNullOrWhiteSpace instead.
• String.Concat and String.Join has new overloads in .NET 4.0, use StringHelper.Concat and StringHelper.Join instead.
• Stopwatch.Restart was added in .NET 4.0, use StopwatchExtensions.Restart instead.
• StringBuilder.Clear was added in .NET 4.0, use StringBuilderExtensions.Clear instead.
• Some methods were added to Task in .NET 4.0, use TaskEx instead. TaskEx has been made available in all .NET versions and is kept consistent with OmerMor/AsyncBridge and the Async CTP.

Note 1: the class ReadOnlyCollection exists since .NET 2.0, it takes a IList<T> instead of ICollection<T> and does not implement IReadOnlyCollection<T> which was added in .NET 4.5 - the class ExtendedReadOnlyColletion<T> aliviates these problems.

Note 2: I have tryied porting to Portable Class Library... the limited reflection left no clear path to port Linq.Expressions and the changes in the threading model would require a rewrite of most of the threading related code.

Others:

• The classes added in .NET 4.5 that require EventHandler<T> without the generic constraint may get backported using Theraot.Core.NewEventHandler<T>. Avoid using EventHandler<T> explicitly in those cases.
• The classes added in .NET 4.0 or .NET 4.5 that require OperationCanceledException.CancellationToken et al. may get backported using Theraot.Core.NewOperationCanceledException. Avoid creating this exceptions yourself.