title: ASP.NET Web API - Getting 404 when posting a Base64 string with HttpClient
body: <p>Not sure what I'm doing wrong here.</p>
  
  <p>Trying to post a Base64 encoded byte array, and getting a 404.</p>
  
  <p>The thing is, when I try it with a normal value ("test"), it works.</p>
  
  <p>API:</p>
  
  <pre><code>[HttpPost]
  public IHttpActionResult Post(dynamic data)
  {
    // ...
    return Ok();
  }
  </code></pre>
  
  <p>Client:</p>
  
  <pre><code>public static bool UploadDocument(string base64Image)
  {
    // ...
    using (var handler = new HttpClientHandler() { UseDefaultCredentials = true})
    using (var client = new HttpClient(handler))
    {
      var data = new { Image = base64Image }; // Image = 123 (or any random value) Works.
      var res = client.PostAsJsonAsync(@"(url)", data).Result;
      if(res.IsSuccessStatusCode)
        // ...
    }
  }
  </code></pre>
  
  <p>Tried a couple other variations, also tried using WebRequest instead.
  The issue remains.</p>