public async void dondeVender()
        {
            var compra = new Compra
            {
                IdCompra = Settings.IdCompra,
            };

            var response = await ApiServices.InsertarAsync <Compra>(compra, new Uri(Constants.BaseApiAddress), "/api/Compras/GetCompra");

            compraresult = JsonConvert.DeserializeObject <Compra>(response.Result.ToString());
            var color = new Color(0, 0, 255, 0.3);

            TK.CustomMap.Position centro = new TK.CustomMap.Position(latitude: compraresult.Latitud.Value, longitude: compraresult.Longitud.Value);
            var circle = new TKCircle {
                Radius = 700, Center = centro, Color = color
            };

            TkCircle.Add(circle);


            VerCompra = true;
            //  CenterSearch = new MapSpan(centro, centro.Latitude, centro.Longitude);

            CenterSearch = (MapSpan.FromCenterAndRadius((new TK.CustomMap.Position(centro.Latitude, centro.Longitude)), Distance.FromMiles(5)));
        }