1
我有这个疑问我不得不删除ORDER BY p.IDC＃字典HashSet的
string query = "SELECT p.Price, p.ID, p.Name, c.Name as CategoryName, p.CategoryID, c.ID AS CategoryPK, c.ParentID,"
+ " o.ID as OrderID,o.ProductID,o.ClientCompanyID,o.Quentity"
+ " FROM Products p LEFT JOIN Categories c ON p.CategoryID=c.ID LEFT JOIN Orders o ON o.ProductID=p.ID ORDER BY p.ID";
，我有这个代码我应该删除，如果where子句中我有最后一个元素与数据库当前元素进行比较。
static List<Product> GetProducts(SqlCommand command)
{
using (SqlDataReader reader = command.ExecuteReader())
{
List<Product> listProducts = new List<Product>();
while (reader.Read())
{
Product product = null;
int productId = (int)reader["ID"];
if (listProducts.Count >= 1 && listProducts[listProducts.Count - 1].ID == productId)
{
product = listProducts[listProducts.Count - 1];
}
if (product == null)
{
product = new Product();
product.ID = productId;
product.Name = (!reader.IsDBNull(reader.GetOrdinal("Name")) ? (string)reader["Name"] : null);
product.Price = reader.GetDecimal(reader.GetOrdinal("Price"));
product.CategoryID = reader.GetInt32(reader.GetOrdinal("CategoryID"));
Category newCat = new Category();
newCat.ID = reader.GetInt32(reader.GetOrdinal("CategoryPK"));
newCat.CategoryName = reader.GetString(reader.GetOrdinal("CategoryName"));
newCat.Parent = (!reader.IsDBNull(reader.GetOrdinal("ParentID")) ? reader.GetInt32(reader.GetOrdinal("ParentID")) : 0);
product.Category = newCat;
}
Order order = new Order();
order.ID = (!reader.IsDBNull(reader.GetOrdinal("OrderID")) ? (int?)reader["OrderID"] : null);
order.ClientCompanyID = (!reader.IsDBNull(reader.GetOrdinal("ClientCompanyID")) ? (int?)reader["ClientCompanyID"] : null);
order.ProductID = (!reader.IsDBNull(reader.GetOrdinal("ProductID")) ? (int?)reader["ProductID"] : null);
order.Quentity = (!reader.IsDBNull(reader.GetOrdinal("Quentity")) ? (int?)reader["Quentity"] : null);
product.Orders.Add(order);
listProducts.Add(product);
}
reader.Close();
listProducts = listProducts.Distinct().ToList();
return listProducts;
}
}
我必须删除订单通过查询，然后使用字典中的方法来从数据库中获得这个数据，但我是新来解释。有人可以帮助我如何做到这一点。谢谢！