问题
I want to map complex object to dapper result from query which has two inner joins. I know we've solution to map one inner join but I want to map two inner joins result.
Here is the Scenario:
My Classes are:
public class Order
{
public int id { get; set; }
public string order_reference { get; set; }
public string order_status { get; set; }
public List<OrderLine> OrderLines { get; set; }
}
public class OrderLine
{
public int id { get; set; }
public int order_id { get; set; }
public string product_number { get; set; }
public List<OrderLineSize> OrderLineSizes { get; set; }
}
public class OrderLineSize
{
public int id { get; set; }
public int order_line_id { get; set; }
public string size_name { get; set; }
}
Order has OrderLines as List and OrderLine as OrderLineSizes as List.
Now, Here is my query base on that I want to populate List<Order> with correct data:
SELECT *
FROM orders_mstr o
INNER JOIN order_lines ol ON o.id = ol.order_id
INNER JOIN order_line_size_relations ols ON ol.id = ols.order_line_id
Here is what I tried so far:
var lookup = new Dictionary<int, Order>();
connection.Query<Order, OrderLine, Order>(@"
SELECT o.*, ol.*
FROM orders_mstr o
INNER JOIN order_lines ol ON o.id = ol.order_id
", (o, ol) => {
Order orderDetail;
if (!lookup.TryGetValue(o.id, out orderDetail))
{
lookup.Add(o.id, orderDetail = o);
}
if (orderDetail.OrderLines == null)
orderDetail.OrderLines = new List<OrderLine>();
orderDetail.OrderLines.Add(ol);
return orderDetail;
}).AsQueryable();
var resultList = lookup.Values;
Using this, I can successfully map order object with OrderLine but I want to populate OrderLineSizes as well with correct data.
回答1:
I tried my best and solve it.
Here is the more easy and accurate solution as per me.:
var lookup = new Dictionary<int, OrderDetail>();
var lookup2 = new Dictionary<int, OrderLine>();
connection.Query<OrderDetail, OrderLine, OrderLineSize, OrderDetail>(@"
SELECT o.*, ol.*, ols.*
FROM orders_mstr o
INNER JOIN order_lines ol ON o.id = ol.order_id
INNER JOIN order_line_size_relations ols ON ol.id = ols.order_line_id
", (o, ol, ols) =>
{
OrderDetail orderDetail;
if (!lookup.TryGetValue(o.id, out orderDetail))
{
lookup.Add(o.id, orderDetail = o);
}
OrderLine orderLine;
if (!lookup2.TryGetValue(ol.id, out orderLine))
{
lookup2.Add(ol.id, orderLine = ol);
orderDetail.OrderLines.Add(orderLine);
}
orderLine.OrderLineSizes.Add(ols);
return orderDetail;
}).AsQueryable();
var resultList = lookup.Values.ToList();
回答2:
I don't know what is class 'OrderDetail' you don't provide it so I used Order class.
This can also be done by QueryMultiple but because your question includes INNER JOIN I don't use it.
public Dictionary<int, Order> GetOrderLookup()
{
var lookup = new Dictionary<int, Order>();
const string sql = @" SELECT o.id,
o.order_reference,
o.order_status,
ol.id,
ol.order_id,
ol.product_number,
ols.id,
ols.order_line_id,
ols.size_name
FROM orders_mstr o
JOIN order_lines ol ON o.id = ol.order_id
JOIN order_line_size_relations ols ON ol.id = ols.order_line_id";
List<Order> orders = null;
using (var connection = OpenConnection(_connectionString))
{
orders = connection.Query<Order, OrderLine, OrderLineSize, Order>(sql, (order, orderLine, orderLizeSize) =>
{
orderLine.OrderLineSizes = new List<OrderLineSize> { orderLizeSize };
order.OrderLines = new List<OrderLine>() { orderLine };
return order;
},
null, commandType: CommandType.Text).ToList();
}
if (orders == null || orders.Count == 0)
{
return lookup;
}
foreach (var order in orders)
{
var contians = lookup.ContainsKey(order.id);
if (contians)
{
var newLinesToAdd = new List<OrderLine>();
var existsLines = lookup[order.id].OrderLines;
foreach (var existsLine in existsLines)
{
foreach (var newLine in order.OrderLines)
{
if (existsLine.id == newLine.id)
{
existsLine.OrderLineSizes.AddRange(newLine.OrderLineSizes);
}
else
{
newLinesToAdd.Add(newLine);
}
}
}
existsLines.AddRange(newLinesToAdd);
}
else
{
lookup.Add(order.id, order);
}
}
return lookup;
}
回答3:
I decided to use Dapper to get a big data for calculating somethings. This is my dapper extension method to join 3 table in _RepositoryBase.cs file.
public List<Tuple<T, T2, T3, T4>> QueryMultiple<T2, T3, T4>(string sql, object param)
where T2 : class
where T3 : class
{
using (var con = new SqlConnection(GetConnStr()))
{
if (con.State == ConnectionState.Closed)
con.Open();
var query = con.Query<T, T2, T3, T4, Tuple<T, T2, T3, T4>>(sql, (t, t2, t3, t4) => Tuple.Create(t, t2, t3, t4), param);
//if (query.Count() == 0)
// return new List<T>();
var data = query.ToList();
con.Close();
con.Dispose();
return data;
}
}
Then, this function will help you to get sql joined data via dapper.
public List<Table1> GetSqlJoinedDataViaDaper(int customerId)
{
var repo = new GenericRepository<T_LOOKUP>();
var sql = @"select table1.ID Table1ID, table1.*,
table2.ID Table2ID, table2.*,
table3.ID Table3ID, table3.*
from dbo.Table1 table1 (nolock)
left outer join dbo.Table2 table2 (nolock) on table2.ID=table1.FKTable2ID
left outer join dbo.Table3 table3 (nolock) on table3.ID=table1.FKTable3ID
where table1.CustomerID=@p1 ";
var resultWithJoin = repo.QueryMultiple<Table1, Table2, Table3>(sql,
new { p1 = 1, splitOn = "Table1ID,Table2ID,Table3ID" }).ToList();
var retval = new List<Table1>();
foreach (var item in resultWithJoin)
{
Table1 t1 = item.Item2; //After first split
t1.Table2 = item.Item3; //After Table2ID split
t1.Table3 = item.Item4; //After Table3ID split
retval.Add(t1);
}
return retval;
}
Summary: Write your select and insert split between tables. Say splits to Dapper and get your data. I used this and worked better than Entity Framework.
来源：https://stackoverflow.com/questions/43973685/dapper-map-multiple-joins-sql-query