为什么这个请求可以使用 HttpWebRequest 而不是 RestSharp？

Question

I am consuming an API that expects a XML in the body request. First i consumed the api via Postman and it worked, then i used that tool of Postman to convert the request to RestCharp C# code, and then using that code the reponse that i was receiving was different compared to postman. After that, i used Fiddler to generate c# code with the postman request, and using that code that fiddler generated i was able to consume the API via code sucessfully. I am just trying to understand what is the difference between the code generated from postman and the code generated from Fiddler.

This is the code that is generated from Fiddler and it works:

            HttpWebRequest request = 
            (HttpWebRequest)WebRequest.Create("http://x.x.x.x.x");

            request.Accept = "*/*";
            request.KeepAlive = true;

            request.Method = "POST";
            request.ServicePoint.Expect100Continue = false;

            byte[] postBytes = System.Text.Encoding.UTF8.GetBytes(body);
            request.ContentLength = postBytes.Length;
            Stream stream = request.GetRequestStream();
            stream.Write(postBytes, 0, postBytes.Length);
            stream.Close();
            response = (HttpWebResponse)request.GetResponse();

This is the code generated from Postman (slightly altered, but still the code that was generated from postman didn't work and i don't think that the changes that was made interfered with the result) using RestSharp that doesn't work:

        var client = new RestClient("http://x.x.x.x.x");

        client.ConfigureWebRequest((r) =>
        {
           r.ServicePoint.Expect100Continue = false;
           r.KeepAlive = true;
        });

        var request = new RestRequest();

        request.AddXmlBody(body);
        IRestResponse response = client.Post(request);
        return response;

I tried a lot of things in the RestSharp code, like adding a header with different content-types and encoding, for example

     request.AddHeader("Content-Type", "text/xml;charset=utf-8");

but nothing worked. The response from the api when consumed by the RestSharp code says it got an error of NPE, which i believe it means NullPointerException, but since the api is working just fine via postman and the code generated by Fiddler, i don't think the problem is in the API. Btw, the parameter body in the code are the exact same in both codes.

Answer 1

It looks like the request body is not matching with expected content type by API. When the content does not match the content type expected by the API then you may get NPE error.

in your fiddler generated code you are sending XML string as text.

Please add the following code:

request.AddHeader("Content-Type", "text/plain");
request.AddParameter("undefined", "<YourXml></YourXml>", ParameterType.RequestBody);

or

request.AddHeader("Content-Type", "application/xml");
request.AddParameter("undefined", "<YourXml></YourXml>", ParameterType.RequestBody);

Instead of

request.AddXmlBody(body);