System Net WebException The remote name could not be resolved

Question

I am testing an endpoint that I am experiencing some issues with   I am simply using HttpClient in a loop that performs a request each hour   var httpClient   new HttpClient    var message   httpClient GetAsync url  Result  Console WriteLine message StatusCode     Once in a while I am getting this exception      System Net Http HttpRequestException  An error occurred while sending   the request  ---  System Net WebException  The remote name could not   be resolved   xxx    The experience is that right after the exception  the URL can be accessed  In a browser you simply refresh the page and all is good   I still haven t got any reports from users experiencing it so I am wondering if it s just a local issue here but could use a little information to help diagnose   Is there a way to check if The remote name could not be resolved is caused by an DNS issue or by a web server issue from the exceptions  Can I get more information out of HttpCLient or do I need more advanced diagnostic tools

User · Answer

Open the hosts file located at     C  windows system32 drivers etc     Hosts file is for what   Add the following at end of this file    YourServerIP    YourDNS  Example   198 168 1 1     maps google com

User · Answer

I had a similar issue when trying to access a service  old ASMX service   The call would work when accessing via an IP however when calling with an alias I would get the remote name could not be resolved    Added the following to the config and it resolved the issue    lt system net gt       lt defaultProxy enabled  true  gt       lt  defaultProxy gt   lt  system net gt

User · Answer

It s probably caused by a local network connectivity issue  but also a DNS error is possible   Unfortunately HResult is generic  however you can determine the exact issue catching HttpRequestException and then inspecting InnerException  if it s a WebException then you can check the WebException Status property  for example WebExceptionStatus NameResolutionFailure should indicate a DNS resolution problem     It may happen  there isn t much you can do   What I d suggest to always wrap that  network related  code in a loop with a try catch block  as also suggested here for other fallible operations   Handle known exceptions  wait a little  say 1000 msec  and try again  for say 3 times   Only if failed all times then you can quit report an error to your users  Very raw example like this   private const int NumberOfRetries   3  private const int DelayOnRetry   1000   public static async Task lt HttpResponseMessage gt  GetFromUrlAsync string url        using  var client   new HttpClient              for  int i 1  i  lt   NumberOfRetries    i                try                   return await client GetAsync url                              catch  Exception e  when  i  lt  NumberOfRetries                    await Task Delay DelayOnRetry

[c#] System.Net.WebException: The remote name could not be resolved:

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