public IHttpActionResult PutTransaction(string id, Transaction transaction)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

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

            try
            {
                rep.Update(id, transaction);
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!rep.TransactionExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return StatusCode(HttpStatusCode.NoContent);
        }
        public IHttpActionResult PostTransaction(Transaction transaction)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            rep.Add(transaction);

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