title: HttpClient not supporting PostAsJsonAsync method & dll in C#
body: <p>I am trying to call a API in my Windows App .Net 4.6.1</p>
  <pre><code>HttpClient client = new HttpClient();
              Uri baseAddress = new Uri(&quot;https://smsmisr.com/&quot;);
              client.BaseAddress = baseAddress;
              var sendtime = DateTime.Now.ToString(&quot;yyyy-MM-dd-HH-mm&quot;);
  
              HttpResponseMessage response = client.PostAsJsonAsync(
              &quot;api/webapi/?&quot; +
              &quot;username=XXXxx&quot; +
              &quot;&amp;password=XXXXXX&quot; +
              &quot;&amp;language= 3 Or 2 Or 1&quot; +
              &quot;&amp;sender=Your Sender &quot; +
              &quot;&amp;mobile=2012XXXXXX, 2011XXXX&quot; +
              &quot;&amp;message=Encoded Message&quot; +
              &quot;&amp;DelayUntil=&quot; + sendtime
              ).Result;
  </code></pre>
  <p>and while writing the code I am getting the error</p>
  <p><strong>Error CS1501  No overload for method 'PostAsJsonAsync' takes 1 arguments</strong></p>
  <p>after searching i added this references :</p>
  <pre><code>using System.Net.Http;
  using System.Net.Http.Headers;
  using System.Net.Http.Formatting.dll;
  </code></pre>
  <p>but this error appear:
  <strong>Error CS0234  The type or namespace name 'dll' does not exist in the namespace 'System.Net.Http.Formatting' (are you missing an assembly reference?)</strong></p>