How to Post JSON data to a Web API using HttpClient
<p>I have the following code, basically it takes in a dynamic object (in this case of type file) and using the <code>HTTPClient</code> class tries to a POST to a <code>WebAPI controller</code>, the issue I am having is that the controller is always getting <code>NULL</code> for the values on my <code>[FromBody]</code> parameter.</p>

<h1>Code</h1>

<pre><code>var obj = new
        {
            f = new File
            {
                Description = description,
                File64 = Convert.ToBase64String(fileContent),
                FileName = fileName,
                VersionName = versionName,
                MimeType = mimeType
            },
        }

var client = new HttpClient(signingHandler)
{
   BaseAddress = new Uri(baseURL + path) //In this case v1/document/checkin/12345
};

client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));                        

HttpResponseMessage response;
action = Uri.EscapeUriString(action);

//Obj is passed into this, currently it is of type File 
var content = new StringContent(JsonConvert.SerializeObject(obj).ToString(),
            Encoding.UTF8, "application/json");

response = client.PostAsync(action, content)).Result;
if (response.IsSuccessStatusCode)
{     
    var responseContent = response.Content;                
    string responseString = responseContent.ReadAsStringAsync().Result;
    return JsonConvert.DeserializeObject&lt;T&gt;(responseString);
}
</code></pre>

<h1>Controller</h1>

<pre><code>[HttpPost]
[Route("v1/document/checkin/{id:int}")]
public void Checkin_V1(int id, [FromBody] File f)
{
        //DO STUFF - f has null on all of its properties
}
</code></pre>

<h1>Model</h1>

<pre><code>public class File
{
    public string FileName { get; set; }
    public string VersionName { get; set; }
    public string Description { get; set; }
    public string MimeType { get; set; }
    public byte[] Bytes { get; set;}
    public string File64 { get; set; }
}
</code></pre>

<p>The model is shared on both the <code>WebAPI</code> and the client app.</p>

<p>Any help on why this is failing would be much appreciated, been going around in circles for a while now.</p>