|
|
|
|
|
|
Author Rank:
|
|
Total page views :
42553
|
|
Total downloads :
676
|
|
|
|
|
Download
Files:
|
|
|
|
|
|
|
|
|
|
|
|
|
Similar ArticlesMost ReadTop RatedLatest
|
|
|
|
|
|
|
|
|
|
Two interesting additions to the 2.0 C# language are the Action<> object, and anonymous methods. The Action<> object lets you specify an action to be performed on an object. And the anonymous method lets you specify a method with no body (thus... the anonymity).
The Action Object
|
public delegate void Action<T>(T obj); |
The Action object is used to perform some action on an object and is a perfect place to use an anonymous method.
If we define a method "Write" that writes the value of an integer to the console, and define a delegate with the same signature as the method
|
private delegate void WriteHandler(int value);
public static void Write(int value)
{
Console.WriteLine("value=" + value.ToString());
} |
We can create a method that returns an Action<int> object that fires the delegate.
|
public static Action<int> WriteMessage()
{
WriteHandler whndl = new WriteHandler(Write);
return new Action<int>(whndl);
} |
And we can wire it up like this
|
public static void Run()
{
Action<int> f = WriteMessage();
int x = 0;
while (x++ <= 5)
{
f(x);
}
} |
And we'll get these results
value=1
value=2
value=3
value=4
value=5
value=6 |
Which in itself is pretty cool, but even better...
We can also do the same thing using an anonymous method and drastically reduce the complexity and amount of code required. An anonymous method is a method with no declaration. Basically the functionality is declared along with the delegate. The sample below will return the same results.
|
class Sample
{
public static void Run()
{
Action<int> f = WriteMessage();
int x = 0;
while (x++ <= 5)
{
f(x);
}
}
public static Action<int> WriteMessage()
{
// Anonymous - no method body declared
return delegate(int value)
{
Console.WriteLine("value=" + value.ToString());
};
}
} |
Notice that the compiler can figure out that an Action<int> object needs to be created in order to be returned and takes care of it.
If you would like to see a real-world application of the Action<> object and anonymous methods, check out this great article on the List<> object by Craig Murphy
A Puzzle
Here's a small puzzle for you involving anonymous methods and the Action<> object. Let's say we have a class with an integer member variable.
|
public class MyObject
{
private int m_value = 0;
public int Value
{
get { return m_value; }
set { m_value = value; }
}
} |
We declare some code to increment the value of our member variable using an anonymous method
|
class Sample
{
public static void Run()
{
MyObject myObj = new MyObject();
Action<MyObject> change = Increment();
while (myObj.Value <= 5)
{
change(myObj);
Console.WriteLine("value=" + myObj.Value.ToString());
}
}
public static Action<MyObject> Increment()
{
return delegate(MyObject i) { i.Value++; };
}
} |
And get the following results.
value=1
value=2
value=3
value=4
value=5
value=6 |
So far so good, right?
Now for the brain teaser.
If run the Run() method in the following code
|
class Sample
{
public static void Run()
{
int i = 1;
Action<int> change = Increment();
for (int x = 0; x < 5; x++ )
{
change(i);
Console.WriteLine("value=" + i.ToString());
}
}
public static Action<int> Increment()
{
return delegate(int i) { i++; };
}
} |
Why do we end up with this result
value=1
value=1
value=1
value=1
value=1
value=1 |
Instead of this one?
value=1
value=2
value=3
value=4
value=5
value=6 |
If you give up and want some help figuring it out, check out these articles:
Article 1 | Article 2
Hope you enjoy the puzzle...
Until next time,
Happy coding
|
|
|
Login
to add your contents and source code to this article
|
|
|
|
|
|
|
|
|
|
|
|
|
|
C# Consulting is founded in 2002 by the founders of C# Corner. Unlike a traditional
consulting company, our consultants are well-known experts in .NET and many of them
are MVPs, authors, and trainers. We specialize in Microsoft .NET development and
utilize Agile Development and Extreme Programming practices to provide fast pace
quick turnaround results. Our software development model is a mix of Agile Development,
traditional SDLC, and Waterfall models.
|
|
Click here to learn more about C# Consulting. |
|
|
|
|
|
|
|
Introducing MaxV - one click. infinite control. Hyper-V Hosting from MaximumASP.
Finally – a virtual platform that delivers next-generation Windows Server 2008 Hyper-V virtualization technology from a managed hosting partner you can truly depend on. Visit www.maximumasp.com/max for a FREE 30 day trial. Hurry offer ends soon.
Climb aboard the MaxV platform and take advantage of High Availability, Intelligent Monitoring, Recurrent Backups, and Scalability – with no hassle or hidden fees.
As a managed hosting partner focused solely on Microsoft technologies since 2000, MaximumASP is uniquely qualified to provide the superior support that our business is built on. Unparalleled expertise with Microsoft technologies lead to working directly with Microsoft as first to offer IIS 7 and SQL 2008 betas in a hosted environment; partnering in the Go Live Program for Hyper-V; and product co-launches built on WS 2008 with Hyper-V technology.
|
Dynamic PDF
ceTE software specializes in components for dynamic PDF generation and manipulation. The DynamicPDF™ product line allows you to dynamically generate PDF documents, merge PDF documents and new content to existing PDF documents from within your applications.
|
Go.NET
Build custom interactive diagrams, network, workflow editors, flowcharts, or software design tools. Includes many predefined kinds of nodes, links, and basic shapes. Supports layers, scrolling, zooming, selection, drag-and-drop, clipboard, in-place editing, tooltips, grids, printing, overview window, palette. 100% implemented in C# as a managed .NET Control. Document/View/Tool architecture with many properties&events. Optional automatic layout.
|
Dundas Software
Dundas Chart for .NET is the most advanced .NET charting package available today. With an extremely complete feature set, elegant architecture and easy implementation, Dundas Chart can quickly add advanced Charting functionality to enhance and transform ASP.NET and Windows Forms applications. Whether you are implementing charting into internal projects, or building applications for clients, Dundas Chart offers advanced technology and advanced results to get the most out of data.
|
Clickatell's SMS Gateway
Clickatell's Developer Solutions allow you to SMS enable any website or
application via a range of API's. Learn More about our API connections.
|
Microsoft Visual Studio 2010 Professional
Microsoft Visual Studio 2010 Professional will launch on April 12, but you can beat the rush and secure your copy today by pre-ordering at the affordable estimated retail price of $549 (US). Pre-order now.
|
Nevron Chart for .NET 2010.1 Now Available
The leading .NET charting control now features PDF, Flash and Silverlight export, visualization of large datasets and more. Deliver true charting functionality to your BI, Scorecard, Presentation or Scientific apps. Download evaluation now.
|
Developer-Ready ASP.NET 2.0 Web Hosting with 3 MONTHS FREE
Now supporting .NET 3.0 Framework with Windows Workflow Foundation, Windows Communication Foundation (WCF), Windows Presentation Foundation (WPF), windows CardSpace (WCS)! Providing more flexibility for Developers with Web Services Support and a User/Permission Manger. Also supporting MS SQL 2005/2000 with Real-Time Backups, FREE Automated Attach .MDF Tool, FREE SQL Restore and Shrink SQL DB Tools, and SQL
|
|
|
|
|
|
|
|
|
|
Download
Files:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|