如何将POST json从C＃发送到asp.net Web API

Question

How is it possible to make a POST request to ASP.Net web api from C#. I have used Newtonsoft dll files to create the json, but, I am not able to send it to the api.

My code is :

        Login login = new Login
        {
            userid = username.Text,
            pass = pass.Text
        };
        string json = JsonConvert.SerializeObject(login, Formatting.Indented);

How to send this json to web api, and get a response ?

Edit

string url = "myurl";


        var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
        httpWebRequest.ContentType = "application/json; charset=utf-8";
        httpWebRequest.Method = "POST";
        httpWebRequest.Accept = "application/json; charset=utf-8";

        using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
        {

            json = json.Replace("\r\n","");
            //json = json.Replace("\",", "\","   + "\"" +"\u002B");
            streamWriter.Write(json);
            streamWriter.Flush();
            streamWriter.Close();
        }

        var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
        using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
        {
            var result = streamReader.ReadToEnd();
            pass.Text = result.ToString();
        }

Answer 1

I made it work, by having a few edits. Instead of directly serializing the json object, I used a class, and assigned values to it, and serialized it using JavaScriptSerializer. Thanks for your help Shekhar.

        var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
        httpWebRequest.ContentType = "application/json; charset=utf-8";
        httpWebRequest.Method = "POST";
        httpWebRequest.Accept = "application/json; charset=utf-8";

        using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
        {
            string loginjson = new JavaScriptSerializer().Serialize(new
            {
                userid = username.Text,
                password = pass.Text
            });

            streamWriter.Write(loginjson);
            streamWriter.Flush();
            streamWriter.Close();

            var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
            using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
            {
                var result = streamReader.ReadToEnd();
                pass.Text = result.ToString();
            }
        }

Answer 2

You can use HttpWebRequest class to create a request and use StreamWriter to write your Json with the request and finally get HttpWebResponse from the Web API.

var httpWebRequest = (HttpWebRequest)WebRequest.Create("path/api");
httpWebRequest.ContentType = "text/json";
httpWebRequest.Method = "POST";
using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
{
   streamWriter.Write(json);
   streamWriter.Flush();
}
var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();

Answer 3

Reg: "How to send this JSON to Web API, and get a response?"

The current existing answers to your question all use .NET's WebRequest ; which is a super frustrating library to work with. I would like to offer the easiest & most concise way of 'sending JSON to Web API'.

Open-source to the rescue. There are three excellent open-source, free NuGet libraries as alternatives. Thank goodness! These are all well supported, documented and easy to work with.

• ServiceStack.Text - fast, light and resilient.
• RestSharp - simple REST and HTTP API Client
• Flurl - a fluent, portable, testable HTTP client library

There is not much between them, but I would give ServiceStack.Text the slight edge …

• Github stars are roughly the same.
• Open Issues & importantly how quickly any issues closed down? ServiceStack takes the award here for the fastest issue resolution & no open issues.
• Documentation? All have great documentation; however, ServiceStack takes it to the next level & is known for its 'Golden standard' for documentation.

Ok - so what does a Post Request in JSON look like within ServiceStack.Text?

var response = "http://example.org/login"
    .PostJsonToUrl(new Login { Userid="admin", Password="mypassword" });

That is one line of code. Concise & easy! Compare the line of code to the overly complicated WebRequest