WebClient vs HttpClient vs HttpWebRequest

转载:http://www.diogonunes.com/blog/webclient-vs-httpclient-vs-httpwebrequest/

Just when I was starting to get used to call WebServices through WSDL – like I showed here and here – I had to call a RESTful API. If you don’t know what I’m talking about you’re like me a week ago. Let’s just say that:

• a WSDL API uses SOAP to exchange XML-encoded data
• a REST API uses HTTP to exchange JSON-encoded data

That’s a whole new paradigm. Instead of GetObject() and SetObject()methods you have a single url api/object that may receive either an HTTP GETrequest or an HTTP POST request.

The .NET framework offers you three different classes to consume REST APIs: HttpWebRequest, WebClient, HttpClient. To worsen your analysis paralysisthe open-source community created yet another library called RestSharp. Fear not, I’ll ease your choice.

In the beginning there was… HttpWebRequest

This is the standard class that the .NET creators originally developed to consume HTTP requests. Using HttpWebRequest gives you control over every aspect of the request/response object, like timeouts, cookies, headers, protocols. Another great thing is that HttpWebRequest class does not block the user interface thread. For instance, while you’re downloading a big file from a sluggish API server, your application’s UI will remain responsive.

However, with great power comes great complexity. In order to make a simple GET you need at least five lines of code; we’ll see WebClient does it in two.

HttpWebRequest http = (HttpWebRequest)WebRequest.Create("http://example.com");
WebResponse response = http.GetResponse();

MemoryStream stream = response.GetResponseStream();
StreamReader sr = new StreamReader(stream);
string content = sr.ReadToEnd();

The number of ways you can make a mistake with HttpWebRequest is truly astounding. Only use HttpWebRequest if you require the additional low-level control that it offers.

WebClient. Simple.

WebClient is a higher-level abstraction built on top of HttpWebRequest to simplify the most common tasks. Using WebClient is potentially slower (on the order of a few milliseconds) than using HttpWebRequest directly. But that “inefficiency” comes with huge benefits: it requires less code, is easier to use, and you’re less likely to make a mistake when using it. That same request example is now as simple as:

var client = new WebClient();
var text = client.DownloadString("http://example.com/page.html");

Note: the using statements from both examples were omitted for brevity. You should definitely dispose your web request objects properly.

Don’t worry, you can still specify timeouts, just make sure you follow this workaround.

HttpClient, the best of both worlds

HttpClient provides powerful functionality with better syntax support for newer threading features, e.g. it supports the await keyword. It also enables threaded downloads of files with better compiler checking and code validation. For a complete listing of the advantages and features of this class make sure you read this SO answer.

The only downfall is that it requires .NET Framework 4.5, which many older or legacy machines might not have.