C# Online Compiler | .NET Fiddle

// @nuget: Newtonsoft.Json
// @nuget: System.Net.Http

using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading;

public class Program
{
	static string _baseURL = "https://sandbox.livevol.com/api/v1/delayed/";
	public static void Main()
	{
		string idServerURL = "https://sandbox.livevol.com/id/connect/token";
		string authenticationHeader = Convert.ToBase64String(Encoding.UTF8.GetBytes("sandbox_api_examples_client:api_example_secret")); // Sandbox
		
		var accessToken = GetBearerToken(idServerURL, authenticationHeader);
		
		if (!string.IsNullOrEmpty(accessToken))
		{
			PostData("trade-review", accessToken);
		}
	}

	static string GetBearerToken(string idServer, string authorization)
	{
		var httpClient = new HttpClient{BaseAddress = new Uri(idServer)};
		Console.Write("Accessing URL: " + idServer + " ...");
		
		httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", authorization);
		HttpResponseMessage response = httpClient.PostAsync(string.Empty, (HttpContent)new FormUrlEncodedContent(new Dictionary<string, string>()
		{{"grant_type", "client_credentials"}}), CancellationToken.None).Result;
		
		if (response.StatusCode == HttpStatusCode.OK)
		{
			var data = response.Content.ReadAsStringAsync().Result;
			var content = JObject.Parse(data);
			Console.WriteLine("successfully received access token...");
			return content.GetValue("access_token").ToString();
		}
		else
		{
			//Add robust response handing
			Console.WriteLine(string.Format("Response status code does not indicate success: {0} ({1})", (int)response.StatusCode, response.ReasonPhrase));
			Console.WriteLine("Did you remember to update the client_id:client_secret?");
			return null;
		}
	}

    static void PostData(string url, string accessToken)
    {
         var httpClient = new System.Net.Http.HttpClient { BaseAddress = new Uri(_baseURL) };
         Console.WriteLine("Accessing URL: " + _baseURL + url);

         httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
         var content = new StringContent("[{\"trade_price\":8.9,\"trade_size\":18,\"time_stamp\":\"2019-01-18 11:45:23.467\",\"expiry\":\"2019-01-18\",\"root\":\"AMZN\",\"strike\":1702.5,\"option_type\":\"C\"}]", System.Text.Encoding.UTF8, "application/json");       
         var response = httpClient.PostAsync(url, content).Result;

         if (response.StatusCode == HttpStatusCode.OK)
         {
             var data = JArray.Parse(response.Content.ReadAsStringAsync().Result);
			 
			 //Write raw results to console	
             Console.WriteLine(data);

         }
         else
         {
             Console.WriteLine(string.Format("Response status code does not indicate success: {0} ({1})", (int)response.StatusCode, response.ReasonPhrase));
         }
     }
	
}

         var content = new StringContent("[{\"trade_price\":8.9,\"trade_size\":18,\"time_stamp\":\"2019-01-18 11:45:23.467\",\"expiry\":\"2019-01-18\",\"root\":\"AMZN\",\"strike\":1702.5,\"option_type\":\"C\"}]", System.Text.Encoding.UTF8, "application/json");       
 
// @nuget: Newtonsoft.Json
// @nuget: System.Net.Http
​
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading;
​
public class Program
{
    static string _baseURL = "https://sandbox.livevol.com/api/v1/delayed/";
    public static void Main()
    {
        string idServerURL = "https://sandbox.livevol.com/id/connect/token";
        string authenticationHeader = Convert.ToBase64String(Encoding.UTF8.GetBytes("sandbox_api_examples_client:api_example_secret")); // Sandbox
        
        var accessToken = GetBearerToken(idServerURL, authenticationHeader);
        
        if (!string.IsNullOrEmpty(accessToken))
        {