异步Web任务返回XML格式的字符串

Question

我希望创建一个异步任务，将从联机API请求数据。 我通过谷歌发现的所有资源并没有帮助我解决这个问题，因此我现在问。

到目前为止，程序很简单，包括：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Xml; 
using System.Threading.Tasks; 
using System.IO; 
using System.Net; 
using System.Net.Http; 
using System.Net.Http.Headers; 
using System.Collections.Specialized; 

class Program 
{ 
    static void Main(string[] args) 
    { 
     Console.WriteLine("Hello, world! Hit ANY key to continue..."); 
     Console.ReadLine(); 
     //Task<string> testgrrr = RunAsync(); 
     //string XMLString = await testgrrr; 
     var XMLString = await RunAsync(); //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'. 
     //Some XML parsing stuff here 
    } 
} 

public async Task<string> RunAsync() 
{ 
    using (var client = new HttpClient()) 
    { 
     var item = new List<KeyValuePair<string, string>>(); 
     item.Add(new KeyValuePair<string, string>("typeid", "34")); 
     item.Add(new KeyValuePair<string, string>("usesystem", "30000142")); 
     var content = new FormUrlEncodedContent(item); 
     // HTTP POST 
     response = await client.PostAsync("", content); 
     if (response.IsSuccessStatusCode) 
     { 
      var data = await response.Content.ReadAsStringAsync(); 
      Console.WriteLine("Data:" + data); 
      return data; //XML formatted string 
     } 
    } 
    return ""; 
} 

我希望能够有并行运行这些web请求的多，让他们返回XML字符串被解析。代码不能与以下错误：

An object reference is required for the non-static field, method, or property 'EVE_API_TestApp.Program.RunAsync()' 
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'. 

我是新来的C＃和异步/等待。任何帮助，将不胜感激！

Answer 1

Main不能标记为async，所以你需要做的是从Main呼叫Task.Wait。这是罕见的例外之一的一般规则，您应该使用await而不是Wait。

static void Main(string[] args) 
{ 
    MainAsync().Wait(); 
} 

static async Task MainAsync() 
{ 
    Console.WriteLine("Hello, world! Hit ANY key to continue..."); 
    Console.ReadLine(); 
    var XMLString = await RunAsync(); 
    //Some XML parsing stuff here 
}