In this article I will explain with an example, how to use HttpClient in ASP.Net Core MVC.
This article will illustrate how to call a JSON REST API using HttpClient and also how to deserialize JSON data to object in ASP.Net Core MVC.
Note: For beginners in ASP.Net MVC Core, please refer my article ASP.Net MVC Core Hello World Tutorial with Sample Program example.
 
 
The ASPSnippets Test REST API
This article uses the following REST API hosted on GitHub.
https://raw.githubusercontent.com/aspsnippets/test/master/Customers.json
 
 
The JSON string returned from the API
The following JSON string is returned from the ASPSnippets Test API.
[
   {
      "CustomerId":1,
      "Name":"John Hammond",
      "Country":"United States"
   },
   {
      "CustomerId":2,
      "Name":"Mudassar Khan",
      "Country":"India"
   },
   {
      "CustomerId":3,
      "Name":"Suzanne Mathews",
      "Country":"France"
   },
   {
      "CustomerId":4,
      "Name":"Robert Schidner",
      "Country":"Russia"
   }
]
 
 
Model
The Model class consists of following properties.
public class CustomerModel
{
    public string CustomerId { get; set; }
    public string Name { get; set; }
    public string Country { get; set; }
}
 
 
Namespaces
You will need to import the following namespaces.
using System.Net;
using System.Net.Http;
using Newtonsoft.Json;
 
 
Controller
The Controller consists of the following Action method.
Action method for handling GET operation
Inside this Action method, first the Security Protocol is set.
Note: SecurityProtocol needs to be set to TLS 1.2 (3072) in order to call an API.
 
Then the API is called using HttpClient and the JSON string is downloaded and deserialized to Generic List collection of CustomerModel class objects.
Finally, the Generic List collection of CustomerModel class objects is returned.
public class HomeController : Controller
{
    public IActionResult Index()
    {
        //Setting TLS 1.2 protocol
        ServicePointManager.Expect100Continue = true;
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
 
        //Fetch the JSON string from URL.
        List<CustomerModel> customers = new List<CustomerModel>();
        string apiUrl = "https://raw.githubusercontent.com/aspsnippets/test/master/Customers.json";
 
        HttpClient client = new HttpClient();
        HttpResponseMessage response = client.GetAsync(apiUrl).Result;
        if (response.IsSuccessStatusCode)
        {
            customers = JsonConvert.DeserializeObject<List<CustomerModel>>(response.Content.ReadAsStringAsync().Result);
        }
 
        //Return the Deserialized JSON object.
        return Json(customers);
    }
}
 
 
Screenshot
Using HttpClient in ASP.Net Core
 
 
Downloads
Download Code