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c# - WebHttpRequest fails (500) while postman successfully runs the web GET request

问题描述

I try to get a specific value from a specific site...

the site periodically updating the value using an Ajax call to https://www.plus500.co.il/api/LiveData/FeedUpdate?instrumentId=19

(you can Navigate to the address and see you get the XML response.)

using Postman: sending 

GET /api/LiveData/FeedUpdate?instrumentId=19 HTTP/1.1
Host: www.plus500.co.il
Cache-Control: no-cache
Postman-Token: f823c87d-3edc-68ce-e1e7-02a8fc68be7a

I get a valid Json Response...

Though, when i try it from C#:

var webRequest = WebRequest.CreateHttp(@"https://www.plus500.co.il/api/LiveData/FeedUpdate?instrumentId=19");
webRequest.Method = "GET";
using (var response = webRequest.GetResponse())
{...}

The request Fails with Error-Code 403 (Forbidden)

when adding:

webRequest.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.84 Safari/537.36";

The request Fails with Error-Code 500 (Internal Server Error)

Addition (Edit)

I also initiate with

ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 |
                                   SecurityProtocolType.Tls11 |
                                   SecurityProtocolType.Tls |
                                   SecurityProtocolType.Ssl3;

Also, I Tried Setting a CookieContainer, but the result is the same 500.

Why is Postman/Chrome Successfuly querying this API while C# Webrequest do not?
What is the difference?

标签： c#ajaxweb-serviceshttpwebrequestpostman

解决方案

因此，失败的原因是默认情况下，来自邮递员的客户端请求中包含标头，尽管不是来自 C# 请求。

使用像 Fiddler ( https://www.telerik.com/fiddler ) 这样的程序，您可以查看请求以查看邮递员请求的标头是：

Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8    
Accept-Encoding: gzip, deflate, br    
Accept-Language: en-US,en;q=0.9    
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.84 Safari/537.36

然而从 C# 开始

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

像这样填写额外的客户端请求标头可以让它顺利通过：

webRequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8";
webRequest.Headers.Add("Accept-Encoding", "gzip deflate,br");
webRequest.Headers.Add("Accept-Language", "en-US,en;q=0.9");

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