c# HttpClient with https gets 400 Bad Request - but http works

Question

I'm trying to get a web request working using HttpClient. It works when using http, but does not work with https. The URL I'm testing with works in a browser with both http and https, however, when using the code below it works only with http.

One of the URLs I test with is one I setup with both http and https. This code has the same problem there as well.

Do I need to add another confuration to make HttpClient work with https?

Note: I have used the proxy below in a Python app and it works for both http and https so the problem is not the proxy.

public static async System.Threading.Tasks.Task Main(string[] args) { var url = "https://www.google.com"; using (System.Net.Http.HttpClientHandler handler = new System.Net.Http.HttpClientHandler() { Proxy = new System.Net.WebProxy(@"http://38.39.202.55:80"), UseProxy = true, }) { using (System.Net.Http.HttpClient hc = new System.Net.Http.HttpClient(handler)) { hc.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; Googlebot/2.1; +http://www.google.com/bot.html)"); string data = ""; using (System.Net.Http.HttpResponseMessage response = await hc.GetAsync(url)) { data = await response.Content.ReadAsStringAsync(); System.Console.WriteLine(data); } System.Console.WriteLine(data); } } }

Thank You

"The URL I'm testing with works in a browser with both http and https" - is that too with a proxy? — user585968
– user585968, Commented May 6, 2021 at 23:17
I think there are is a cookie that is causing confusion. What you posted is not consistent. So I recommend repeating your test and between each test go into a browser and manually delete all cookies. — jdweng
– jdweng, Commented May 7, 2021 at 0:00
OK my browser comment was confusing. What I meant by that is some websites accept only http or https. the browser test was to verify that the website runs on both meaning that the c# code above should work. — spacedog
– spacedog, Commented May 7, 2021 at 4:13

Milot Thaci · Accepted Answer · 2021-05-07 00:22:47Z

It may have to do with the verification of ssl certificates. Thus, for example, you could edit the web.config file to bypass ssl errors. Like this:

 <system.net> <settings> <servicePointManager checkCertificateName="false" checkCertificateRevocationList="false" /> </settings> </system.net>

This is a console app so I added the config data into the app.config directly below <configuration> and it did not work. Same result.

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