public async Task Update(Contractor item)
        {
            using (var dataContext = new ContractorsDataContext())
            {
                dataContext.Entry(item).State = EntityState.Modified;

                await dataContext.SaveChangesAsync();
            }
        }
        public async Task Add(Contractor item)
        {
            using (var dataContext = new ContractorsDataContext())
            {
                dataContext.Contractors.Add(item);

                await dataContext.SaveChangesAsync();
            }
        }