C# 如何使用web客户端解析json并在控制台中显示它？

错误消息显示：

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“System.Net.WebClient”不包含“DownloadString”的定义，并且找不到接受“System.Net.WebClient”类型的第一个参数的扩展方法“DownloadString”（您是否缺少using指令或程序集引用？

在windows phone中，在大多数情况下，您被迫以异步方式编程。 因此，您必须使用DownloadStringAsync，而不是DownloadString，如本示例所示：

WebClient client = new WebClient();

string value = client.DownloadString("http://www.onemap.sg/publictransportation/service1.svc/routesolns?token=qo/s2TnSUmfLz+32CvLC4RMVkzEFYjxqyti1KhByvEacEdMWBpCuSSQ+IFRT84QjGPBCuz/cBom8PfSm3GjEsGc8PkdEEOEr&sl=39167.4524,35518.8625&el=28987.5163,33530.5653&startstop=&endstop=&walkdist=300&mode=bus&routeopt=cheapest&retgeo=true&maxsolns=1&callback=");

 // Write values.
 Console.WriteLine("Results:");
 Console.WriteLine(value.Length);
 Console.WriteLine(value);

资料来源：

您需要使用System.Net.Http添加

，并使用System.Net.Http.Header添加

我没有在您的特定场景或服务中测试过这一点，但我不明白为什么它不适用于您，因为它是异步获取JSON的

  var client = new WebClient();

  client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(loadHTMLCallback);
  client.DownloadStringAsync(new Uri("http://www.myurl.com/myFile.txt"));
//...

public void loadHTMLCallback(Object sender, DownloadStringCompletedEventArgs e)
{
  var textData = (string)e.Result;
  // Do cool stuff with result
  Debug.WriteLine(textData);
}

//Initialize new Client
HttpClient client = new HttpClient();

//Response will handle the returned JSON
HttpResponseMessage response;

//URI of the service
string strURI = "http://www.onemap.sg/publictransportation/service1.svc/routesolns?token=qo/s2TnSUmfLz+32CvLC4RMVkzEFYjxqyti1KhByvEacEdMWBpCuSSQ+IFRT84QjGPBCuz/cBom8PfSm3GjEsGc8PkdEEOEr&sl=39167.4524,35518.8625&el=28987.5163,33530.5653&startstop=&endstop=&walkdist=300&mode=bus&routeopt=cheapest&retgeo=true&maxsolns=1&callback=";

//String that the response will be converted to.
string strResponseJSONContent = "";

//Lets the client know to expect JSON
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

//Getting the JSON and saving it to response
response = client.GetAsync(strURI).Result;

//Setting response to a string
strResponseJSONContent = response.Content.ReadAsStringAsync().Result;