public IHttpActionResult PutVenta(int id, Venta venta)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            if (id != venta.id)
            {
                return BadRequest();
            }

            db.Entry(venta).State = EntityState.Modified;

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!VentaExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return StatusCode(HttpStatusCode.NoContent);
        }
        public IHttpActionResult PostVenta(Venta venta)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            db.Ventas.Add(venta);
            db.SaveChanges();

            return CreatedAtRoute("DefaultApi", new { id = venta.id }, venta);
        }