post data to API

I am trying to post data to my API. Could anyone tell me where I missing??

I am getting error at:

Here is my code:

var client = new HttpClient();
client.BaseAddress = new Uri("http://Ipaddress/apiName");
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Authorization = CreateBasicHeader(userName, password);
var data = new
{
data = "0001"
};
HttpResponseMessage responseFinal = null;
responseFinal = client.PutAsJsonAsync("apiName/api/blabla", data).Result; // I am getting error

Advance thanks,

Darma