HttpClient class is used to send the http request and receive http response by URL.
It is defined inside the System.Net.Http namespace.
HttpClient is instantiated  once and re-used throughout the life of an application.

Properties:
It contains a following properties:

1. BaseAddress:- This property is used to get or set the base address of Uniform Resource Identifier (URI) of the Internet resource used while sending a request.
2. DefaultRequestHeaders:- This property is used to get the header which is used to sent with each request.
3. Timeout:- This property is used to get or set the number of milliseconds to wait before the request times out.

We are assuming a class "Company"

Code for class company:

Class Company
{
int Id {get;set;} 
string Company{get;set;}
}

To Initialize the HttpClient instance, See the below code

HttpClient client = New HttpClient();
client.BaseAddress = New Uri("http://localhost:52084/");
client.DefaultRequestHeaders.Accept.Add(New MediaTypeWithQualityHeaderValue("application/json"))

To send the Get request, See the below code

Company company=null;
 var url = "Service1.svc/GetCompanies";
 HttpResponseMessage response = client.GetAsync(url).Result;
if (response.IsSuccessStatusCode) 
{
   var myobject = response.Content.ReadAsStringAsync().Result;                    
company= JsonConvert.DeserializeObject<Company>(myobject);
}

To send a Post request, See the below code

Company company=new Company{ Company="ABCD" };
var url = "Service1.svc/SaveCompany";
var json = JsonConvert.SerializeObject(company);
var companyString = New StringContent(json, Encoding.UTF8, "application/json");
HttpResponseMessage response= client.PostAsync(url, companyString).Result;
if (response.IsSuccessStatusCode) 
{
  var myobject = response.Content.ReadAsStringAsync().Result;                  
  result = JsonConvert.DeserializeObject<Company>(myobject);
}