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I have the following WebClient inside my asp.net mvc web application:

using (WebClient wc = new WebClient()) // call the Third Party API to get the account id 
{
     string url = currentURL + "resources/" + ResourceID + "/accounts?AUTHTOKEN=" + pmtoken;
     var json = await wc.DownloadStringTaskAsync(url);
 }

So can anyone advice how I can change it from WebClient to be HttpClient?

john Gu
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    All the cool kids are using HttpClient now. This is a wrapper around WebRequest and provides an easier model to work with. – Ananke Oct 08 '15 at 16:24
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    @Ananke ok so can you adivce how to change WebClient to be HttpClient ? – john Gu Oct 08 '15 at 17:02

1 Answers1

31

You can write the following code:

string url = 'some url';

// best practice to create one HttpClient per Application and inject it
HttpClient client = new HttpClient();

using (HttpResponseMessage response = client.GetAsync(url).Result)
{
    using (HttpContent content = response.Content)
    {
         var json = content.ReadAsStringAsync().Result;
    }
}

Update 1 :

if you want to replace the calling to Result property with the await Keyword, then this is possible, but you have to put this code in a method which marked as async as following

public async Task AsyncMethod()
{
    string url = 'some url';

    // best practice to create one HttpClient per Application and inject it
    HttpClient client = new HttpClient();

    using (HttpResponseMessage response = await client.GetAsync(url))
    {
        using (HttpContent content = response.Content)
        {
           var json = await content.ReadAsStringAsync();
        }
     }
}

if you missed the async keyword from the method, you could get a Compile-time error like the following

The 'await' operator can only be used within an async method. Consider marking this method with the 'async' modifier and changing its return type to 'Task<System.Threading.Tasks.Task>'.

Update 2 :

Responding to your original question about converting the 'WebClient' to 'WebRequest' this is the code that you could use, ... But Microsoft ( and me ) recommended you to use the first approach (by using the HttpClient).

string url = currentURL + "resources/" + ResourceID + "/accounts?AUTHTOKEN=" + pmtoken;

HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
httpWebRequest.Method = "GET";

using (WebResponse response = httpWebRequest.GetResponse())
{
     HttpWebResponse httpResponse = response as HttpWebResponse;
     using (StreamReader reader = new StreamReader(httpResponse.GetResponseStream()))
     {
         var json = reader.ReadToEnd();
     }
}

if you use C# 8 and above, then you can write very elegant code

public async Task AsyncMethod()
{
    string url = 'some url';

    // best practice to create one HttpClient per Application and inject it
    HttpClient client = new HttpClient();

    using HttpResponseMessage response = await client.GetAsync(url);
    using HttpContent content = response.Content;
    var json = await content.ReadAsStringAsync();
}   // dispose will be called here, when you exit of the method, be aware of that

Update 3

To know why is HttpClient is more recommended than WebRequest and WebClient you can consult the following links.

Deciding between HttpClient and WebClient

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

HttpClient vs HttpWebRequest

What difference is there between WebClient and HTTPWebRequest classes in .NET?

http://blogs.msdn.com/b/henrikn/archive/2012/02/11/httpclient-is-here.aspx

Hakan Fıstık
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  • thanks for the reply,, but will there be any problem if i replace the .Result with await in your code? – john Gu Oct 09 '15 at 15:30
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    @johnG plz see the updated answer to handle the 'await' instead of 'Result' property. – Hakan Fıstık Oct 09 '15 at 15:45
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    @johnG I also add an update for the 'WebRequest' class. – Hakan Fıstık Oct 09 '15 at 16:00
  • thanks for the reply,, but why it is recommended to use HttpClient, i did not get your point .. thanks ... – john Gu Oct 09 '15 at 16:46
  • @johnG I updated the answer, please consider this answer as accepted if it is really solve your problem. – Hakan Fıstık Oct 09 '15 at 16:57
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    Wrapping `HttpClient` in a `using` block is bad. Please don't do this. See the link below for a detailed explanation of why. Long story short, `HttpClient` was designed to be used as a single instance throughout your application. It handles opening and closing sockets for you. By wrapping it in a `using` block, it gets disposed after, and won't close the socket like it's supposed to. This can result in the system running out of sockets once a certain threshold of requests per second is met. https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/ – Anthony Stivers Feb 17 '19 at 11:41
  • @AnthonyStivers absolutely true. it defeats the purpose. – SRIDHARAN Oct 13 '20 at 11:56
  • I think any class that implements IDisposable should be kept in a using block and that everything else should result in a compilation error. If HttpClient wants to do some smart socket reuse, it can still do so by not disposing everything in the Dispose method. – Anders Lindén Nov 23 '20 at 09:44