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

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:

<system.net>
    <defaultProxy enabled="true">
    </defaultProxy>
</system.net>

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

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

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

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