Jan 4

Feliz año Nuevo

Uncategorized Comments Off

Feliz Navidad y Feliz Año Nuevo

Jan 4

Happy new year

General General Comments Off

I wish you a happy new year 2012.

S.

Feb 11

The TDD Compare to SOLID

Tests Design, SOLID, TDD Comments Off

In his article, Mark Seemann [1] deals with the TDD approach, and he wondered if the TDD is a good design Method. For attempting to answer this question, his compare TDD to S.O.L.I.D. design.

References :

[1] : Mark Seemann – The TDD apostate

Feb 11

Asynchronous Programming in C# by Eric Lippert

Thread Async, parallel programming Comments Off

I just found a great series of articles about Asynchronous Programming in C# [1].

Summary :

References :

[1] Eric Lippert : Asynchronous Programming in C#, The Series

Nov 3

NotifyingObject for WPF & Silverlight

WPF NotifyingObject, WPF Comments Off

Today, I read an excellent article about NotifyingObject on WPF, Tomer Shamam [1] provides a very nice solution to use the NotifyingObject with lambda expressions.

He adds some nice features like callback, coercing, validation, and other goodies from WPF DependencyProperty.

References :
[1] : Tomer Shamam, NotifyingObject for WPF & Silverlight

Oct 30

Make non-threadsafe code threadsafe

Framework .NET .NET, Framework, Thread Comments Off

In his weblog, Jeffrey Richter [1] explains that a customer wanted to increase the performance of his code and the best way to accomplish this was to have multiple threads processing their own data independently of each other. But, again, the class library code base would produce errant results if we did this.

In this excellent article, Jeffrey Richter demonstrated the problem of data isolation in multi-threaded environment. Two distinct sources (threads) want to change the same data. To simulate this, both threads use a static generic list.

To correct the problem, Jeffrey Richter uses proxies over AppDomain (see the Chris Brumme article [2]) for isolation. I think that it’s a great job to isolate data and it’s a good pattern to do this.

However in this case, we have another way to correct  the data isolation problem by using the [TreadStatic] attribut. A static field marked with ThreadStaticAttribute is not shared between threads. Each executing thread has a separate instance of the field, and independently sets and gets values for that field. If the field is accessed on a different thread, it will contain a different value.

Do not specify initial values for fields marked with ThreadStaticAttribute, because such initialization occurs only once, when the class constructor executes, and therefore affects only one thread. If you do not specify an initial value, you can rely on the field being initialized to its default value if it is a value type, or to a null reference if it is a reference type.

I would like to illustrate this with the exemple below :

Source code

class Program
{
	static void Main(string[] args)
	{
		ThreadPool.QueueUserWorkItem( (object target) => { NonConcurrentAlgorithm.Add("Item1"); } );
		NonConcurrentAlgorithm.Add("Item2");
		Thread.Sleep(1000); // To demonstrate the problem has been fixed
		NonConcurrentAlgorithm.GetItems().ForEach( (String name) => { Console.WriteLine(name); } );
		Console.WriteLine("Appuyer sur une touche pour quitter.");
		Console.ReadLine();
 
		/* This code will produce output similar to the following:
		* Item2
		* Appuyer sur une touche pour quitter. */
	}
}
 
internal static class NonConcurrentAlgorithm
{
	[ThreadStatic]
	private static List _items=null;
	private static List Items
	{
		get
		{
			if (_items == null) _items = new List();
			return _items;
		}
	}
	public static void Add(String item)
	{
		Items.Add(item);
	}
	public static List GetItems()
	{
		return Items;
	}
}

[1] : Using AppDomains to make Non-Threadsafe code Threadsafe

[2] : AppDomains (“application domains”)

[3] : A tale of two techniques: The [ThreadStatic] Attribute and System.Web.HttpContext.Current.Items

Oct 28

Mocks, stubs, fakes & dummies

Tests Mocks, Stubs, TDD Comments Off

This terms are often use in TDD, but many people mix up this terms.  In his article (based upon Gerard Meszaros’s  book [3]) Martin Fowler [1] explains the main difference between them.

Jeremy D. Miller [4]  capsulated this idea  by “state_based testing vs interaction testing” :

“The real difference between a mock and a stub is in the style of unit testing, i.e. state-based testing versus interaction testing.  A stub is a class that is hard-coded to return data from its methods and properties.  You use stubs inside unit tests when you’re testing that a class or method derives the expected output for a known input.

A mock object is a tool for interaction based testing.  You use a mock object to record and verify the interaction between two classes.  Roy Osherove made my all time favorite explanation of mock objects by comparing a mock object to a spy that listens to the interaction between two classes.”

Roy Osherove [2] provided a good scheme of the difference in flow information (see below)

Framework .NET for Mocking, Stubing & Faking :

• FakeItEasy
• NMock
• EasyMock.NET
• TypeMock Isolator Commercial / Paid
• Rhino Mocks
• Moq
• NSubstitute
• NMock3 based upon NMock, add lambda expressions

References :

[1] : Martin Fowler, Mocks Aren’t Stubs

[2] : Roy Osherove, Mocks and Stubs – The difference is in the flow of information

[3]  : Gerard Meszaros, XUnit Test Patterns

[4] : Jeremy D. Miller, Mock Objects and Stubs: The Bottle Brush of TDD

Oct 27

La validation de couches dans VS 2010

Visual studio 2010 Architecture, layer validation, Visual studio 2010 Comments Off