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in my C# project, I added a web reference from the internet. It was added correctly.
But when I call the web service's functions, it will crash! with this error exception:
The remote server returned an unexpected response: (407) Proxy Authentication Required ( The ISA Server requires authorization to fulfill the request. Access to the Web Proxy filter is denied.  ).

I changed the 'LAN settings' in Internet Options, and Unchecked the boxes 'Use automatic configuration script' and 'Use a proxy server for your LAN' .
It would have this error exception:
There was no endpoint listening at http:// ... 
Updated 24-May-22 22:49pm

If above doesn't work and want to handle proxy in code

If you're using HttpClient then consider this.
HttpClientHandler handler = new HttpClientHandler();
IWebProxy proxy = WebRequest.GetSystemWebProxy();
proxy.Credentials = CredentialCache.DefaultCredentials;
handler.Proxy = proxy;

var client = new HttpClient(handler);
// your next steps...

And if you're using HttpWebRequest:
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri + _endpoint);
IWebProxy proxy = WebRequest.GetSystemWebProxy();
proxy.Credentials = CredentialCache.DefaultCredentials;
request.Proxy = proxy;

Kind referencce:
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Richard MacCutchan 27-Jun-20 5:33am    
As you can see the questioner solved his problem five years ago.
My problem was solved by writing this code in app.config of my c# project, into configuration tag:
  <defaultproxy usedefaultcredentials="true" />
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The CredentialCache method above (Solution 2) did not work for me (maybe a different authentication type?).

The useedfaultcredentials method (Solution 1) did work and can be implemented in code thus:

HttpWebRequest request = WebRequest.CreateHttp(uri)

WebProxy proxy = new WebProxy();
proxy.UseDefaultCredentials = true;
request.Proxy = proxy;

Documentation : WebProxy.UseDefaultCredentials

Hope that helps someone out - I couldn't find it mentioned anywhere in these sort of questions.
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