Download pdf - 25 things i’ve learned about c#

Phil [email protected]

http://philknows.net

» Desktops ˃ WinForm

˃ WPF

˃ Linux, Mac, Solaris

» Servers˃ Web Apps

˃ Services (web/native)

» Embedded Systems˃ Micro .NET (Netduino, FEZ Domino)

˃ Windows Phone

˃ Robots

˃ iPhone

» Gaming Consoles˃ Xbox 360

˃ Wii, Playstation 3 (via Mono)

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25 Things I've Learned about C# - Phil Denoncourt

http://mono-project.com

» C# compiles to bytecode˃ So it must be slow

» Bytecode gets compiled to native code upon first usage˃ Takes advantage of features that machine’s processor

» Matches C++ in Int math, trig, and I/O.˃ Little slower in floating point

» C# benefits from disposing of objects when idle˃ rather than when object is no longer used.

» http://www.osnews.com/story/5602&page=3

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» Built into the framework since 3.0˃ Add reference to System.Speech

» Recognition˃ Command based

˃ Dictation

» Synthesis

» Requires SAPI˃ Windows Vista and Later

˃ Office 2003 and Later

» http://gotspeech.net

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» It’s easy to write˃ ThreadPool.QueueUserWorkItem

˃ PLINQ

˃ BackgroundWorker component

» It’s hard to debug˃ Add trace / logging to your code

» Make sure your classes are “ThreadSafe”˃ Lock keyword

˃ Interlocked class

» http://www.bluebytesoftware.com/blog/

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» Added in 3.0. Implemented as a generic class˃ Allows you to consider value types that are nullable

» Add ? to end of type˃ Int?

˃ DateTime?

˃ String is already a reference type, thus already nullable

» Null Coalesce operator˃ Substitutes a value if the object is null

˃ Really low in operator precedence. Often need parens.

» http://msdn.microsoft.com/en-us/library/1t3y8s4s.aspx

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» Exceptions hold a lot of information

» Throwing them is computationally expensive˃ Avoid using exceptions as logic flow

» Stack trace line numbers are available if PDBs are present with the binaries

» There is a difference between˃ throw

˃ throw ex;

» http://msdn.microsoft.com/en-us/library/5b2yeyab(v=VS.100).aspx

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» checked˃ By default, overflow checking is disabled in C#

+ Depending on compiler options

˃ Placing statements in checked block enables checking

˃ There is also an unchecked keyword

˃ http://msdn.microsoft.com/en-us/library/74b4xzyw(v=VS.100).aspx

» volatile˃ Keyword that indicates field could be updated by multiple threads

+ Disables compiler optimizations that assume single threaded access

˃ Places a “lock” statement around access to the field

˃ http://msdn.microsoft.com/en-us/library/x13ttww7(v=VS.100).aspx

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» Allows you to add new methods to existing classes˃ Even sealed classes

» Can operate on public members˃ But not private members

» Good way to add “missing” functionality to class˃ Good way to make something unmaintainable

» Internally – implemented as a static method passing in the current instance.

» http://extensionmethod.net/

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http://extensionmethod.net/

» Generic template that defers initialization until used

» System.Lazy<T>

» Object will be initialized when the value member is accessed, or ToString() is called.

» http://weblogs.asp.net/gunnarpeipman/archive/2009/05/19/net-framework-4-0-using-system-lazy-lt-t-gt.aspx

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» Lambda operator =>

» Anonymous function˃ Contains code

» Returns a delegate

» Used extensively in Linq

» http://msdn.microsoft.com/en-us/library/bb311046.aspx

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» Eliminates a lot of repetitive coding» Implemented as extension methods in

System.Linq.dll» Must reference the assembly, and add a using

statement:˃ using System.Linq;

» Different providers allow access to different types of data by exposing IQueryable interface˃ Linq to Objects˃ Linq to SQL˃ Linq to Entities˃ Linq to Xml

» http://msdn.microsoft.com/en-us/netframework/aa904594.aspx

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» Normally static fields exist once per AppDomain

» [ThreadStatic] static fields exist once per Thread

» Static constructors and initializers still only execute once.˃ So you have to make sure the object is not null before using it

» http://blogs.msdn.com/b/jfoscoding/archive/2006/07/18/670497.aspx

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» Allows you to move a class from one assembly to another without breaking callers

» [assembly:TypeForwardedTo(typeof(classThatWasMoved)]˃ Place this statement in the original assembly, which must reference

the new assembly.

» Used for refactoring types into different assemblies, and not have to rebuild the caller assembly.˃ Namespace and name can’t change

» Can also redirect entire assembly in .config file˃ assemblyBinding section

» http://msdn.microsoft.com/en-us/library/ms404275.aspx

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» Don’t need to be based on int˃ Can be byte, sbyte, short, ushort, int, uint, long, or ulong.

» If you use the FlagsAttribute, you can perform bitwise operations˃ Meaning that you can store more than one state in an enum variable.

» http://dotnetperls.com/enum-flags

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» -In addition to allowing shortcuts to namespaces

» Automatically disposes objects when scope is outside of the using statement.

» Object doesn’t need to be instantiated in the using statement˃ But should

» More than one object can be tracked by a using statement˃ But they must be of the same type

» http://msdn.microsoft.com/en-us/library/yh598w02.aspx

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» Allows you to examine metadata about compiled code.

» Has a reputation for being slow˃ I haven’t found that to be very true

» Allows access to private methods / fields of a class

» You can also get the actual IL of the method for reverse engineering˃ Which is what Reflector does

» http://msdn.microsoft.com/en-us/library/f7ykdhsy(v=VS.100).aspx

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» Can call other constructor methods˃ Add :this to call a constructor in the current object

˃ Add :base to call a constructor in the base object

» http://msdn.microsoft.com/en-us/library/ms173115.aspx

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» Allows you to write code against an abstract type˃ Type Parameter

» When generic is used, a type is specified. ˃ Reduces the amount of boxing

» Generics can be applied to˃ Classes

˃ Delegates

˃ Methods

˃ Interfaces

» Instead of comparing to null, compare to default(t)» http://msdn.microsoft.com/en-

us/library/512aeb7t(v=VS.100).aspx

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» Allows you to constrain what types can be used with a generic

» Can constrain˃ Classes that implement an interface

˃ Classes must have a common base class

˃ Parameterless constructor

˃ That the type is a class

˃ That the type is a struct

» Constraints enforced by the compiler» http://msdn.microsoft.com/en-us/library/d5x73970.aspx

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» Very easy since .NET 2.0˃ No more worrying about holding onto disposable objects

» File class – static methods for ˃ Copying˃ Renaming˃ Deleting˃ Checking existing˃ Reading /writing data to a file˃ Encrypt/Decrypt a file˃ http://msdn.microsoft.com/en-us/library/system.io.file.aspx

» Path class – static methods for ˃ Assembling a filename˃ Changing extensions˃ Getting a truly temporary filename˃ http://msdn.microsoft.com/en-us/library/system.io.path.aspx

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http://msdn.microsoft.com/en-us/library/system.io.file.aspx

http://msdn.microsoft.com/en-us/library/system.io.path.aspx

» Mostly done for you

» .NET 4.0 supports 354 different cultures

» Allows you to properly˃ Format numbers

˃ Format currency

˃ Format date/times

˃ Compare strings

» By default, the culture of the current thread is used when formatting/comparing

» Globalization != Localization» http://en.wikibooks.org/wiki/.NET_Development_Foundation/Glo

balization

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» You can write code that writes code

» Emits C# or VB.Net

» Or can build an assembly using a compiler

» Can build the assembly in memory˃ Doesn’t get written to disk.

» http://www.15seconds.com/issue/020917.htm

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http://www.15seconds.com/issue/020917.htm

» GZipStream class only compresses one file

» System.IO.Packaging˃ Add reference to “WindowsBase”

» Add each file as part of the package

» It will add a [Content_Types].xml file to every zip file˃ Part of the open packaging specification

» http://madprops.org/blog/zip-your-streams-with-system-io-packaging/

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» Goto in switch statement

» >> multiplies by powers of 2, << divides˃ Real fast

» as operator˃ Faster than cast, doesn’t throw exception

» @ string constant qualifier˃ Ignores \ escapes

» StringBuilder concatenates strings faster˃ For only for large amounts of data

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» Code Access Security

» Strong names

» Lackluster support for Xml Documentation

» Lack of development in certain libraries˃ Linq to SQL

˃ ASP.NET

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