This document summarizes news and features in C# and .NET 4.0, including named and default method parameters, interoperability with dynamic languages via the Dynamic Language Runtime (DLR), generics covariance and contravariance, exceptions handling improvements, application dump debugging, code contracts, application domain profiling, enhanced garbage collection, parallel computing features like Parallel LINQ and the Task Parallel Library, and references for further information. Key topics covered are using dynamic for interoperability while avoiding performance penalties, handling corrupted state exceptions, debugging .NET 4.0 application dumps in Visual Studio 2010, and demonstrations of threading constructs, PLINQ, TPL, and the unified cancellation model.

1. News in C# and NET 4.0Iaşi, 20 februarie 2010Florin Cardaşim, www.rms.ro

2. Agenda

3. C# 4 named and default paramsNamed method parametersDefault method parameter values

4. C# 4 & DLRInterop via Dynamic Language RuntimeDynamically-TypedRubyPythonStatically-TypedVBDynamic Language RuntimeC#Common Language Runtime

5. C# 4 & the DLR: dynamicInterop with dynamic languages like Ruby, PythonInterop with COM

6. C# 4 – DLR Support: dynamicInterop always comes with a performance cost, so do not use dynamic if you don’t really need it

7. C# 4 – DLR Support: dynamicDon’t abuse dynamic in C# because you loose:compile time type checking and intellisense

8. runtime performanceUse dynamic where appropriate

9. C# 4 & the DLRSystem.Numerics.BigIntegerSystem.Numerics.ComplexSystem.TuplesTuple.Create(1,2,3,4,5,6,7,8) - maximum 8 members!!Property names are Item1, Item2, .., Item8 – ugly!Can be used as method params and return valuesCan be inheritedCan be extended by extension methodsSpecifically useful in F#I’ll probably NOT use it in C# http://msdn.microsoft.com/en-us/vcsharp/ee957397.aspx

10. Generics Covariance & Contravariance

11. Generics Co&Contravariancehttp://msdn.microsoft.com/en-us/library/dd799517(VS.100).aspx

12. Exceptions ManagementThis code is bad!WHY?!!!

13. Exceptions ManagementWhat is the problem?(Exception ex) might be a Corrupted State Exception (CSE) , like Access Violation, Invalid Memory, Divide By Zero, Stack OverflowWhat to do if Exception is CSE?Your process and data are in danger. ABORT.Are other actions possible?What is CLR 4.0 doing?CLR 4.0 will NOT deliver CSEs to our code by defaultcatch(Exception ex) will NOT catch the CSEYour process will ABORT

14. Exceptions ManagementFor backwards compatibility useOr at application level

15. Exceptions ManagementA bit of history:CLR1.1: unhandled exceptions (on secondary threads) will NOT abort process

16. CLR 2.0: unhandled exception on secondary will ABORT the process

17. CLR 4.0: CSEs not handled by catch(Exception), process will ABORTConclusions:Do not handle exceptions if you don’t know how

18. ABORT is better than a corrupted processExceptions ManagementConclusions:Only catch exceptions that you can handle

19. ABORT is better than a corrupted process

20. If your process ABORTs than there is a bug somewhere. GO FIX IT!

21. If you really need CSEs in your code use: [HandleProcessCorruptedStateExceptions]Or legacyCorruptedStateExceptionsPolicy enabled="true“

22. Net 4.0 application dump debuggingWhen do we need a dumpCrash, hang, performance analysis etcHow to collect a dumpadplus.vbs, DebugDiag etcTask Manager/Create Dump FileVS2010/Debug/Save Dump As…How to analyze the dumpUntil now windbgonly for native appsNow VS2010 knows to debug .NET 4.0 app dump

23. Net 4.0 dump debuggingDump debugging with WinDbg

24. Net 4.0 dump debugging

25. Code ContractsUntil CLR 4.0Code comments

26. Debug.Assert, Argument validation: if-then-throw

27. Unit tests? In CLR 4.0 we have System.Diagnostics.ContractsPreconditions

28. Required before a method can run

29. Postconditions