c# – 对REST服务的WebClient调用在控制台应用程序中有效,但在as

发布时间：2020-12-15 22:13:30 所属栏目：百科来源：网络整理

导读：我正在调用一个测试REST Web服务,它基本上将一个字符串作为输入,并将其回送给调用者.我在C#控制台应用程序中有以下代码： static async Task RunAsync(){ using (var client = new HttpClient()) { string baseAddress = "http://74.120.219.166/Services/On

我正在调用一个测试REST Web服务,它基本上将一个字符串作为输入,并将其回送给调用者.我在C#控制台应用程序中有以下代码：

static async Task RunAsync()
{
    using (var client = new HttpClient())
    {
    string baseAddress = 
    "http://74.120.219.166/Services/OnyxCloudSyncService.svc/pingSync";
    client.BaseAddress = new Uri(baseAddress); 
    client.DefaultRequestHeaders.Accept.Clear();
    client.DefaultRequestHeaders.Accept.Add(new
       MediaTypeWithQualityHeaderValue("application/json"));
    HttpResponseMessage response = await 
               client.GetAsync("?sampleJson={SAMPLEJSON}");           
    if (response.IsSuccessStatusCode)
    {
        string txtBlock = await response.Content.ReadAsStringAsync(); 
        Console.WriteLine(txtBlock);
        Console.ReadKey();
    }
    }
}

此代码运行完美.但是当我基本上将相同的代码复制到ASP.NET页面的代码隐藏中时,我对服务的调用超时：

using (var SyncClient = new HttpClient())
  {
   string baseAddress = "http://74.120.219.166/Services/OnyxCloudSyncService.svc/pingSync";
   SyncClient.DefaultRequestHeaders.Accept.Clear();
   SyncClient.DefaultRequestHeaders.Accept.Add(new
           MediaTypeWithQualityHeaderValue("application/json"));
   HttpResponseMessage response = await 
          SyncClient.GetAsync("?sampleJson={SAMPLEJSON}");
   if (response.IsSuccessStatusCode)
   {
    string txtBlock = await response.Content.ReadAsStringAsync();
    Response.Write(txtBlock);
    Response.End();
   }
   else
   {
    Response.Write("Error Calling service");
    Response.End();
   }
  }

我从这个页面得到的错误是：

System.Net.Sockets.SocketException: A connection attempt failed because
the connected party did not properly respond after a period of time,or
established connection failed because connected host has failed to respond
74.120.219.166:80.

我是否需要在WebClient上设置某种类型的设置或选项,使其在ASP页面中工作,就像在Console App中一样？我不知道为什么这可以在控制台应用程序中工作,而不是在ASP.NET网页中.

解决方法

您可能遇到问题,因为没有等待结果,可以在 http://www.hanselman.com/blog/TheMagicOfUsingAsynchronousMethodsInASPNET45PlusAnImportantGotcha.aspx找到解决方案

我假设你使用的是.NET 4.5.
将方法编辑为实例,而不是静态,因为您将无法访问Response对象：

async Task RunAsync()
{
    using (var client = new HttpClient())
    {
        string baseAddress =
        "http://74.120.219.166/Services/OnyxCloudSyncService.svc/pingSync";
        client.BaseAddress = new Uri(baseAddress);
        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new
           MediaTypeWithQualityHeaderValue("application/json"));
        HttpResponseMessage response = await
                   client.GetAsync("?sampleJson={SAMPLEJSON}");
        if (response.IsSuccessStatusCode)
        {
            string txtBlock = await response.Content.ReadAsStringAsync();
            Response.Write(txtBlock);
            Response.End();
        }
        else
        {
            Response.Write("Error Calling service");
            Response.End();
        }
    }
}

运行方法如：RegisterAsyncTask(new PageAsyncTask(RunAsync));在.aspx页面的Page指令中输入Async =“true”.我尝试了这种方法,它按预期工作.

（编辑：李大同）

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