POSTing JsonObject With HttpClient From Web API

Question

I'm trying to POST a JsonObject using HttpClient from Web API. I'm not quite sure how to go about this and can't find much in the way of sample code.

Here's what I have so far:

var myObject = (dynamic)new JsonObject();
myObject.Data = "some data";
myObject.Data2 = "some more data";

HttpClient httpClient = new HttpClient("myurl");
httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

HttpResponseMessage response = httpClient.Post("", ???);

I think I need to cast my JsonObject as a StreamContent but I'm getting hung up on that step.

Answer 1

With the new version of HttpClient and without the WebApi package it would be:

var content = new StringContent(jsonObject.ToString(), Encoding.UTF8, "application/json");
var result = client.PostAsync(url, content).Result;

Or if you want it async:

var result = await client.PostAsync(url, content);

Answer 2

The easiest way is to use a StringContent, with the JSON representation of your JSON object.

httpClient.Post(
    "",
    new StringContent(
        myObject.ToString(),
        Encoding.UTF8,
        "application/json"));

Answer 3

Depending on your .NET version you could also use HttpClientExtensions.PostAsJsonAsync method.

https://msdn.microsoft.com/en-us/library/system.net.http.httpclientextensions.postasjsonasync.aspx

Answer 4

If using Newtonsoft.Json:

using Newtonsoft.Json;
using System.Net.Http;
using System.Text;

public static class Extensions
{
    public static StringContent AsJson(this object o)
        => new StringContent(JsonConvert.SerializeObject(o), Encoding.UTF8, "application/json");
}

Example:

var httpClient = new HttpClient();
var url = "https://www.duolingo.com/2016-04-13/login?fields=";
var data = new { identifier = "username", password = "password" };
var result = await httpClient.PostAsync(url, data.AsJson())

Answer 5

I don't have enough reputation to add a comment on the answer from pomber so I'm posting another answer. Using pomber's approach I kept receiving a "400 Bad Request" response from an API I was POSTing my JSON request to (Visual Studio 2017, .NET 4.6.2). Eventually the problem was traced to the "Content-Type" header produced by StringContent() being incorrect (see https://github.com/dotnet/corefx/issues/7864).

tl;dr

Use pomber's answer with an extra line to correctly set the header on the request:

var content = new StringContent(jsonObject.ToString(), Encoding.UTF8, "application/json");
content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
var result = client.PostAsync(url, content).Result;

Answer 6

the code over it in vbnet:

dim FeToSend as new (object--> define class)

Dim client As New HttpClient
Dim content = New StringContent(FeToSend.ToString(), Encoding.UTF8,"application/json")
content.Headers.ContentType = New MediaTypeHeaderValue( "application/json" )
Dim risp = client.PostAsync(Chiamata, content).Result

msgbox(risp.tostring)

Hope this help