C Sharp

GET

using System.Threading.Tasks;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text.Json;

namespace WebApiRequest
{
  class testATM
  {
    private static readonly HttpClient client = new HttpClient();

    private static async Task AtmHttpRequest()
    {
      client.DefaultRequestHeaders.Accept.Clear();
      client.DefaultRequestHeaders.Add("apiKey", "< YOURTOKEN >");

      var bodyContent = new StringContent("{
        \"options\": {
          \"method\": \"GET\",
          \"headers\": {
            \"Content-Type\": \"application/json\",
            \"Accept\": \"application/json\"
          }
        },
        \"url\": \"/rest/api/3/issue/Dev-16\"
      }", System.Text.Encoding.UTF8, "application/json");

      var response = await client.PostAsync(new Uri("<YOUR ENDPOINT URL>"),bodyContent);

      string responseString = await response.Content.ReadAsStringAsync();

      Console.WriteLine(responseString);
    }

    static async Task Main (string[] arg){
      await AtmHttpRequest();
    }
  }
}

POST

using System.Threading.Tasks;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text.Json;

namespace WebApiRequest
{
  class testATM
  {
    private static readonly HttpClient client = new HttpClient();

    private static async Task AtmHttpRequest()
    {
      client.DefaultRequestHeaders.Accept.Clear();
      client.DefaultRequestHeaders.Add("apiKey", "< YOURTOKEN >");

      var bodyContent = new StringContent("{
      \"options\": {
         \"method\": \"POST\",
         \"headers\": {
          \"Content-Type\": \"application/json\",
          \"Accept\": \"application/json\"
        },
        \"body\": {
          \"fields\": {
            \"project\":{
              \"name\": \"<your project name>\"
            },
            \"summary\": \"Create Issue via POST.\",
            \"description\": \"Creating of an issue via a POST request using the API Key Manager\",
            \"issuetype\": {
              \"id\": \"<your issue type id>\"
            }
          }
        }
      },
      \"url\": \"/rest/api/2/issue\"
    }", System.Text.Encoding.UTF8, "application/json");

      var response = await client.PostAsync(new Uri("<YOUR ENDPOINT URL>"),bodyContent);

      string responseString = await response.Content.ReadAsStringAsync();

      Console.WriteLine(responseString);
    }

    static async Task Main (string[] arg){
      await AtmHttpRequest();
    }
  }
}