How to set the Content-Type header for an HttpClient request

var client = new HttpClient();
client.BaseAddress = new Uri("http://example.com/");

// ACCEPT header

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

var request = new HttpRequestMessage(HttpMethod.Post, "relativeAddress");

// CONTENT-TYPE header

request.Content = new StringContent("{\"name\":\"John Doe\",\"age\":33}", 
                     Encoding.UTF8, "application/json");

client.SendAsync(request).ContinueWith(responseTask => 
        Console.WriteLine("Response: {0}", responseTask.Result); );