这是代码

using (HttpClient client = new HttpClient())
{       
    // This url is just for testing and the file really exist 
    byte[] data = client.GetByteArrayAsync("http://pngimg.com/uploads/simpsons/simpsons_PNG96.png").Result; // Returning error 404 here only on IIS

    using (MemoryStream mem = new MemoryStream(data))
    {
        using (var myImg = Image.FromStream(mem))
        {
            // If you want it as Png
            myImg .Save("path_to_your_file.png",ImageFormat.Png);
        }
    }
}

这在IIS Express中有效，但在IIS服务器上返回错误404。我试图从VS进行调试，但使用IIS（Windows 10Pro），它无法正常工作，在IIS（Windows Server 2016）上部署时也无法正常工作。

该应用程序是基于.NET Core 2.1构建的Web服务。

我是否在IIS或应用程序设置中缺少某些内容才能使其正常工作？

我也尝试以下代码：

               using (WebClient client1 = new WebClient())
            {
               var a =  client1.DownloadData(new Uri("http://pngimg.com/uploads/simpsons/simpsons_PNG96.png"));
            }

但是我得到相同的结果。

在这两个代码中，我使用IIS Express和VS都获得了200 OK，并且使用Visual Studio调试中的IIS获得了以下结果：

 ((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).CharacterSet   "iso-8859-1"    string
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).ContentEncoding null    string
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).ContentLength   309 long
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).ContentType "text/html; charset=iso-8859-1" string
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).Cookies {System.Net.CookieCollection}   System.Net.CookieCollection
((System.Net.WebException)e).Response   {System.Net.Httpwebresponse}    System.Net.webresponse {System.Net.Httpwebresponse}
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).Headers {Date: Fri,15 Nov 2019 17:46:35 GMT
Server: Apache/2.2.15,(CentOS)
Connection: close
Content-Length: 309
Content-Type: text/html; charset=iso-8859-1
}   System.Net.WebHeaderCollection
((System.Net.WebException)e).Response.IsFromCache   false   bool
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).IsMutuallyAuthenticated false   bool
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).LastModified    {2019-11-15 1:09:53 PM} System.DateTime
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).Method  "GET"   string
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).ProtocolVersion {1.1}   System.Version
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).ResponseUri {http://pngimg.com/uploads/simpsons/simpsons_PNG96.png} System.Uri
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).Server  "Apache/2.2.15,(CentOS)"   string
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).StatusCode  NotFound    System.Net.HttpStatusCode
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).StatusDescription   "Not Found" string
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response).SupportsHeaders true    bool
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response)._characterSet   "iso-8859-1"    string
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response)._cookies    {System.Net.CookieCollection}   System.Net.CookieCollection
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response)._httpResponseMessage    {StatusCode: 404,ReasonPhrase: 'Not Found',Version: 1.1,Content: System.Net.Http.HttpConnection+HttpConnectionResponseContent,Headers:
{
  Date: Fri,15 Nov 2019 17:46:35 GMT
  Server: Apache/2.2.15
  Server: (CentOS)
  Connection: close
  Content-Length: 309
  Content-Type: text/html; charset=iso-8859-1
}}  System.Net.Http.HttpResponseMessage
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response)._isVersionHttp11    true    bool
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response)._requesturi {http://pngimg.com/uploads/simpsons/simpsons_PNG96.png} System.Uri
((System.Net.Httpwebresponse)((System.Net.WebException)e).Response)._webHeaderCollection    {Date: Fri,(CentOS)
Connection: close
Content-Length: 309
Content-Type: text/html; charset=iso-8859-1
}   System.Net.WebHeaderCollection

编辑：添加图片例外

错误表单http请求：

  

（（（System.aggregateexception）e）。消息“发生一个或多个错误。（响应状态码不表示成功：404（未找到）。）”字符串