private async void guardar_estacion(object sender, EventArgs e)
        {
            var        uri      = new Uri("https://iotsmartp.azurewebsites.net/test_put");
            HttpClient myClient = new HttpClient();

            App.stations guardarestacion = new App.stations()
            {
                _id = App.tem_Id, title = txttitle.Text, description = txtdescription.Text, user = App.tem_user
            };
            string              json     = JsonConvert.SerializeObject(guardarestacion);
            StringContent       content  = new StringContent(json, Encoding.UTF8, "application/json");
            HttpResponseMessage response = null;

            response = await myClient.PutAsync(uri, content);

            await Navigation.PopAsync();
        }
        private async void eliminar_estacion(object sender, EventArgs e)
        {
            HttpClient myClient = new HttpClient();

            App.stations eliminarestacion = new App.stations()
            {
                _id = App.tem_Id
            };
            string json = JsonConvert.SerializeObject(eliminarestacion);

            //            HttpResponseMessage response = null;

            HttpRequestMessage request = new HttpRequestMessage
            {
                Content    = new StringContent(json, Encoding.UTF8, "application/json"),
                Method     = HttpMethod.Delete,
                RequestUri = new Uri("https://iotsmartp.azurewebsites.net/test_delete")
            };
            await myClient.SendAsync(request);

            await Navigation.PopAsync();
        }