const string userName = "usuario";
    const string password = "miclave";
    const string apiBaseUri = "https://ose-gw1.efact.pe:443/api-efact-ose/oauth";
    const string apiGetPeoplePath = "/api-efact-ose/oauth";
    const string authorization = "Y2xpZW50OnNlY3JldA==";
    const string tempurl = "D:\SENDSUNAT\doc.txt";

    static void Main(string[] args)
    {
        //OBTENER EL TOKEN
        var token = GetAPIToken(userName, password, apiBaseUri).Result;
        Console.WriteLine("Token: {0}", token);

        //HACER EL LLAMADO
        var response = GetRequest(token, apiBaseUri, apiGetPeoplePath).Result;
        Console.WriteLine("response: {0}", response);

        //ESPERAR LA CLAVE
        Console.ReadKey();
    }

    private static async Task<string> GetAPIToken(string userName, string password, string apiBaseUri)
    {
        //WebRequest request = WebRequest.Create(apiBaseUri);
        using (var client = new HttpClient())
        {
            //AUTHORIZATION
            //var header = request.Headers["Authorization"];
            //header.StartsWith("Basic " + authorization);

            //SETUP CLIENTE
            client.BaseAddress = new Uri(apiBaseUri);
            client.DefaultRequestHeaders.Accept.Clear();
            //client.DefaultRequestHeaders.GetType = new
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", authorization);
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            //SETUP LOGIN DATA
            var formContent = new FormUrlEncodedContent(new[]
            {
                new KeyValuePair<string, string>("grant_type", "password"),
                new KeyValuePair<string, string>("username", userName),
                new KeyValuePair<string, string>("password", password),
            });

            //ENVIAR REQUEST
            HttpResponseMessage response = await client.PostAsync("/Token", formContent);


            //OBTENER EL ACCESO TOKEN DEL RESPONSE BODY
            var responseJson = await response.Content.ReadAsStringAsync();
            var jObject = JObject.Parse(responseJson);
            return jObject.GetValue("access_token").ToString();
        }
    }

    static async Task<string> GetRequest(string token, string apiBaseUri, string requestPath)
    {
        using (var client = new HttpClient())
        {
            //SETUP CLIENTE
            client.BaseAddress = new Uri(apiBaseUri);
            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(tempurl));
            client.DefaultRequestHeaders.Add("Authorization", "Bearer " + token);

            //HACER EL REQUEST
            HttpResponseMessage response = await client.GetAsync(requestPath);
            var responseString = await response.Content.ReadAsStringAsync();
            return responseString;
        }
    }