In my last post I discussed about how to call and get Google Analytics Reports in C# application. While it works fine mostly, you might encounter following exception if you are behind a proxy

System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: The remote server returned an error: (407) Proxy Authentication Required.
   at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context)
   at System.Net.Http.HttpClientHandler.GetRequestStreamCallback(IAsyncResult ar)
   --- End of inner exception stack trace ---
   at Google.Apis.Http.ConfigurableMessageHandler.<SendAsync>d__59.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Google.Apis.Auth.OAuth2.Requests.TokenRequestExtenstions.<ExecuteAsync>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Google.Apis.Auth.OAuth2.ServiceAccountCredential.<RequestAccessTokenAsync>d__19.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Google.Apis.Auth.OAuth2.ServiceCredential.<GetAccessTokenForRequestAsync>d__23.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Google.Apis.Auth.OAuth2.ServiceAccountCredential.<GetAccessTokenForRequestAsync>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Google.Apis.Auth.OAuth2.ServiceCredential.<InterceptAsync>d__21.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
   at Google.Apis.Http.ConfigurableMessageHandler.<SendAsync>d__59.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Google.Apis.Requests.ClientServiceRequest`1.<ExecuteUnparsedAsync>d__33.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Google.Apis.Requests.ClientServiceRequest`1.Execute()

As Google Analytics Reporting API call involves HttpWebRequest internally, adding following configuration to Web.config will resolve the issue

<system.net>
   <defaultProxy>
     <proxy usesystemdefault="True" />
   </defaultProxy>
</system.net>

Your final Web.config will look like this

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="KeyFileName" value="Your key file name here"/>
    <add key="ViewId" value="Your ViewId here"/>
  </appSettings>
  <system.net>
    <defaultProxy>
      <proxy usesystemdefault="True" />
    </defaultProxy>
  </system.net>
  <startup> 
     <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
  </startup>
</configuration>