HTTP Request works in Postman, but not in C# code

Question

I want to do a simple HTTP request in C#, but something is not working and all I got is 403 Forbidden status code.

When I try to do same request in Postman, everything works fine. I tried to run Fiddler and see all headers that are being sent by Postman. I copy-pasted all of them, but i still got 403 Forbidden in the request sent by C# code.

C# Code (Using https://flurl.dev):

public static void Main(string[] args)
{
    FlurlHttp.Configure(settings => {
        settings.HttpClientFactory = new MyClientFactory();
    });

    var url = "https://example.com"
        .AppendPathSegments(new[] { "v1", "oauth", "accesstoken" })
        .SetQueryParam("grant_type", "client_credentials")
        .AllowAnyHttpStatus()
        .WithBasicAuth("username", "password")
        .WithHeaders(new {
            User_Agent = "Something/0.4.0 Dalvik/2.1.0 (Linux; U; Android 5.1.1; SM-G975F Build/NRD90M)",
            X_Secret_Header = "secret_encoded_value",
            accept_encoding = "gzip, deflate",
            Accept = "*/*"
        });

    HttpResponseMessage msg = url.GetAsync().Result;

    Console.WriteLine("StatusCodeString: " + msg.StatusCode.ToString());
    Console.WriteLine();
    Console.WriteLine(msg.Content.ReadAsStringAsync().Result);
}

class MyClientFactory : DefaultHttpClientFactory
{
    public override HttpMessageHandler CreateMessageHandler()
    {
        return new HttpClientHandler
        {
            AllowAutoRedirect = false
        };
    }
}

C# Request And Response:

Postman Request And Response:

Can someone explain me why is this not working? Same headers, same everything.

I replaced the url with "example.com" because i don't want to show the real API URL here.

Also sorry for so many images.. I don't know how to show the problem here in other way.

Answer 1

From Postman there should be a link on the right side called code. Click that and then select C# to get the code generated by Postman. Paste that in and try it out.

Answer 2

For me the problem was the TLS settings in C#. Try adding this line at the start of your app or just before your HTTP request code:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

Answer 3

I know this old, but to get the same C# code as postman sent, let the postman generate the code for, but first you must get RestSharp lib from nuget or from PM console type this:

Install-Package RestRequest -Version 1.2.0

Steps:

1- Call your rest api from postman

2- Press the code button 3-A pop-up window will open, then choose whatever language you want, in your case it's C#