public List <Product> GetAll()
 {
     using (BTK_ETradeContext context = new BTK_ETradeContext())
     {
         return(context.Products.ToList());
     }
 }
 public void Add(Product product)
 {
     using (BTK_ETradeContext context = new BTK_ETradeContext())
     {
         context.Products.Add(product);
         context.SaveChanges();
     }
 }
 public void Delete(Product product)
 {
     using (BTK_ETradeContext context = new BTK_ETradeContext())
     {
         var entity = context.Entry(product);
         entity.State = EntityState.Deleted;
         context.SaveChanges();
     }
 }