Get data from external API with a asp.net core API

You could use an HttpClient instance to achieve what you want. However, I always find easier to use RestSharp though.

That, of course will depend on your constraints but assuming you have none for this case, you could use RestSharp to make the call to the external API:

Install it:

Install-Package RestSharp

Usage:

using RestSharp;[HttpGet("{id}", Name = "GetRanking")]public async Task<IActionResult> GetByIdAync(long id){    var client = new RestClient($"http://api.football-data.org/v1/competitions/{id}/leagueTable");    var request = new RestRequest(Method.GET);    IRestResponse response = await client.ExecuteAsync(request);    //TODO: transform the response here to suit your needs    return Ok(data);}

To consume the rest response from RestSharp you must use the response.Content property.

You could, for example, deserialize it to Json, manipulate it to fit your needs and return the required data to your API caller.

Example:

Let's say I'd like to get the rankings for the Premier League 2017/18 (Id = 445):

I'll get a lot of help below from the legendary Newtonsoft.Json package and a little of jpath syntax but I'll assume you've already used both :)

Create a couple models to hold the values to be returned to the API caller:

public class LeagueTableModel{    public string LeagueCaption { get; set; }    public IEnumerable<StandingModel> Standings { get; set; }}public class StandingModel{    public string TeamName { get; set; }    public int Position { get; set; }}

Implement the below method in the service class, injected to your controller through DI/IoC to avoid coupling and increase testability (as we all know we should do right?). I'm assuming this class is RankingRepository in your sample:

public RankingRepository: IRankingRepository {    public Task<LeagueTableModel> GetRankingsAsync(long id)    {        var client = new RestClient($"http://api.football-data.org/v1/competitions/{id}/leagueTable");        var request = new RestRequest(Method.GET);        IRestResponse response = await client.ExecuteAsync(request);        if (response.IsSuccessful)        {            var content = JsonConvert.DeserializeObject<JToken>(response.Content);            //Get the league caption            var leagueCaption = content["leagueCaption"].Value<string>();            //Get the standings for the league.            var rankings = content.SelectTokens("standing[*]")                .Select(team => new StandingModel                {                    TeamName = (string)team["teamName"],                    Position = (int)team["position"]                })                .ToList();            //return the model to my caller.            return new LeagueTableModel            {                LeagueCaption = leagueCaption,                Standings = rankings            };        }        //TODO: log error, throw exception or do other stuffs for failed requests here.        Console.WriteLine(response.Content);        return null;    }}

Use it from the controller:

[Route("api/[Controller]")]public class RankingsController : Controller{    private readonly IRankingRepository _rankingRepository;    public RankingsController(IRankingRepository rankingRepo)    {        _rankingRepository = rankingRepo;    }    [HttpGet("{id}", Name = "GetRanking")]    public Task<IActionResult> GetByIdAsync(long id)        //Here is where I want to make the requisition        var model = await _rankingRepository.GetRankingsAsync(id);        //Validate if null        if (model == null)            return NotFound(); //or any other error code accordingly. Bad request is a strong candidate also.        return Ok(model);    }}

Hope this helps!