HttpClient

• HttpClient is intended to be instantiated once and reused throughout the life of an application.
• The following conditions can result in SocketException errors:
  • Creating a new HttpClient instance per request.
  • Server under heavy load.
• Creating a new HttpClient instance per request can exhaust the available sockets.
• The following code initializes the HttpClient instance:

client.BaseAddress = new Uri("<http://localhost:64195/>");
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

GET Request

• The GetAsync method sends the HTTP GET request.
• When the method completes, it returns an HttpResponseMessage that contains the HTTP response.
• If the status code in the response is a success code, the response body contains the JSON representation of a product.
• Call ReadAsAsync to deserialize the JSON payload to a Product instance.
• The ReadAsAsync method is asynchronous because the response body can be arbitrarily large.
• HttpClient does not throw an exception when the HTTP response contains an error code.
• Instead, the IsSuccessStatusCode property is false if the status is an error code.
• If you prefer to treat HTTP error codes as exceptions, call **HttpResponseMessage.EnsureSuccessStatusCode** on the response object.
• EnsureSuccessStatusCode throws an exception if the status code falls outside the range 200–299.
• Note that HttpClient can throw exceptions for other reasons — for example, if the request times out.

Product product = null;
HttpResponseMessage response = await client.GetAsync("api/products/1");
if (response.IsSuccessStatusCode)
	product = await response.Content.ReadAsAsync<Product>();

• When ReadAsAsync is called with no parameters, it uses a default set of media formatters to read the response body.
  • The default formatters support JSON, XML, and Form-url-encoded data.

var formatters = new List<MediaTypeFormatter>
{
    new MyCustomFormatter(),
    new JsonMediaTypeFormatter(),
    new XmlMediaTypeFormatter()
};
response.Content.ReadAsAsync<IEnumerable<Product>>(formatters);