C#

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        string token = "SEU_TOKEN";
        string ticker = "PETR4";
        string url = $"https://brapi.dev/api/quote/{ticker}?token={token}";

        using HttpClient client = new HttpClient();
        string response = await client.GetStringAsync(url);
        Console.WriteLine(response);
    }
}

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

public class Quote
{
    public string Symbol { get; set; }
    public string ShortName { get; set; }
    public decimal RegularMarketPrice { get; set; }
    public decimal RegularMarketChangePercent { get; set; }
    public string Currency { get; set; }
}

public class QuoteResponse
{
    public Quote[] Results { get; set; }
}

public class BrapiClient
{
    private readonly HttpClient _httpClient;
    private readonly string _token;
    private const string BaseUrl = "https://brapi.dev/api";

    public BrapiClient(string token)
    {
        _token = token;
        _httpClient = new HttpClient
        {
            Timeout = TimeSpan.FromSeconds(10)
        };
    }

    public async Task<Quote> GetQuoteAsync(string ticker)
    {
        var url = $"{BaseUrl}/quote/{ticker}?token={_token}";
        var response = await _httpClient.GetStringAsync(url);
        var data = JsonSerializer.Deserialize<QuoteResponse>(response);
        return data?.Results?[0];
    }

    static async Task Main()
    {
        var client = new BrapiClient("SEU_TOKEN");
        var quote = await client.GetQuoteAsync("PETR4");
        
        if (quote != null)
        {
            Console.WriteLine($"{quote.Symbol}: R$ {quote.RegularMarketPrice:F2}");
        }
    }
}