如何用 HttpClient 替換 WebClient？

我的 asp.net mvc Web 應用程序中有以下 WebClient：

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);
}

那麼任何人都可以建議我如何將它從 WebClient 更改為 HttpClient 嗎？

您可以編寫以下程式碼：

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;
   }
}

更新 1：

如果您想Result用關鍵字替換對屬性的呼叫await，那麼這是可能的，但是您必須將此程式碼放在標記為async如下的方法中

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();
       }
    }
}

如果你錯過了async方法中的關鍵字，你可能會得到一個編譯時錯誤，如下所示

‘await’ 運算符只能在非同步方法中使用。考慮使用“async”修飾符標記此方法並將其返回類型更改為“Task<System.Threading.Tasks.Task>”。

更新 2：

回答有關將“WebClient”轉換為“WebRequest”的原始問題，這是您可以使用的程式碼，……但微軟（和我）建議您使用第一種方法（通過使用 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();
    }
}

如果您使用 C# 8 及更高版本，那麼您可以編寫非常優雅的程式碼

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

更新 3

要知道為什麼HttpClient更推薦WebRequest，WebClient您可以查閱以下連結。

在 HttpClient 和 WebClient 之間做出決定

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

HttpClient 與 HttpWebRequest

.NET 中的 WebClient 和 HTTPWebRequest 類有什麼區別？

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

引用自：https://stackoverflow.com/questions/33020657