instagram 3.2 download

Name: instagram 3.2 download
Category: Download
Published: rentveletong1973
Language: English

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Simply Genius .NET.
Software that makes you smile.
The Progress Reporting Pattern in C# 5 async.
Downloads.
Table of Contents.
Introduction.
This article is about the new TAP - the T ask-based A synchronous P attern - and concentrates on the support for progress reporting .
I explain a simple program that gets text from a web server asynchronously. As I show each layer of the solution, I explain the implementation and framework support. I will assume you already know how async and await work.
Firstly, I will show you how simple this has become for application developers. Then I will go under the hood and explore the implementation of a TAP method with progress reporting.
The Requirement.
I have hosted a page on my web server that shows a short list of trite quotes, generated randomly from a list I obtained. The page takes 7 seconds to generate a list of 8 quotes. Each quote is flushed to the network as it is generated, one per second.
The requirement is to write an application that consumes this service and shows both the current progress percentage and all the quotes as soon as they arrive from the ether.
The Client.
I wrote a WinForms app as the client. Here is the entire code for the main Form :
There is quite a lot going on here. I will explain each piece in turn.
Shown event handler.
I am using a lambda to handle this event. Notice that you can use async and await here too, not just for named methods.
The method that does the work, DownloadAsync() , eventually returns a string . When this method completes, the handler just appends "Done!" to the result and shows that. This is how I know the whole process has finished.
Doing the work.
The work is done by an extension method on the WebClient class: DownloadStringTaskAsyncEx . This is also a TAP method, so I can use await to yield control while it is executing.
It takes a URI and returns a string - all well and good. But it also takes an object called progress as a parameter. This is the new pattern for progress reporting.
The progress event.
I'll fudge a little bit here and gloss over the implementation of the progress object. It uses some new classes in .NET 4.5 and deserves a section to itself.
Just assume I have some progress object:
All I need to tell you now is that it has a ProgressChanged event that is raised by the TAP method at suitable points during its execution. This event will be raised on the UI thread, and the e parameter will be an instance of my DownloadStringTaskAsyncExProgress class that contains info about the current progress. So, all I need to do is add a handler that updates my UI controls:
Well, now we have our client code, so now for the fun bit.
The TAP method.
There is a new TAP method on WebClient , but it doesn't take an IProgress parameter and doesn't give access to the response stream, so it doesn't meet the requirements.
However, there is another new TAP method on WebClient that returns a Stream :
And the Stream class also has some new TAP methods. Here is the one I need:
Implementation.
I used these two methods to write the implementation of DownloadStringTaskAsyncEx , with progress reporting that includes the result text as it arrives.
Here is the entire source:
This TAP method also happens to be an async method. This is perfectly correct and allowed me to use the TAP forms of WebClient.OpenRead and Stream.Read . This means that there is no blocking in the method and so it is safe to execute on the UI thread.
One interesting detail is that I must create a new instance of DownloadStringTaskAsyncExProgress each time I call progress.Report() . This is because the ProgressChanged event is marshalled on to the UI thread by using SynchronizationContext.Post() . If I tried to reuse a single Progress object, there would be a race condition between the event handlers and the next call to Report() .
That's all there is to it: the caller creates an IProgress object and passes it in and all the TAP method has to do is call Report() .
The Progress object.
So what is this magic progress object? There are a few new types we need to look at here.
IProgress.
The signature for DownloadStringTaskAsyncEx actually takes an IProgress . This is a new interface in .NET 4.5, defined in the mscorlib.dll assembly.
It only has one method: void Report( T value ) . Remember, an object that implements this interface is passed into the TAP method. The implementation can call the Report method of this object when it wants to report progress.
Progress.
Now I need to create the progress object, so I need a class that implements the interface.
Fortunately, there is an implementation of IProgress in the framework, called just Progress . It is also in mscorlib.dll and here it is:
Basically, when you instantiate this class, it captures the current thread's SynchronizationContext . Then, each time Report is called from inside the TAP method, it raises the ProgressChanged event on the right thread.
Note that Report() uses a SynchronizationContext.Post() . This is why you would get a race condition between previous events being handled and subsequent calls to Report , if you reused your value objects ( instances of T ) in your TAP method.
Conclusion.
As I have shown, the new T ask-based A synchronous P attern makes this sort of code much easier to write - and read. Consumers of TAP methods are almost trivial. Even if you have to write a method TAP yourself, it is still quite simple if you know the patterns.
The async and await keywords just work. Anders and the team have done a great job. The arduous bit for Microsoft was implementing TAP versions of the methods in the framework that block on IO. Application developers can now give their users more information about what an app is doing in an increasingly asynchronous world.
Well, that's it. I hope you have enjoyed reading this article. Thanks.
License.
This article, along with any associated source code and files, is licensed under The Code Project Open License.
Contact.
If you have any feedback, please feel free to contact me.

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