C# Linq加入iquery，如何使用defaultifempty
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Linq join iquery, how to use defaultifempty
提问by user1032957
I have written a linq join query and I would like to take the values, if one of them are empty...
我写了一个 linq join 查询，如果其中一个为空，我想获取这些值...
Code:
代码：
var Details =
UnitOfWork.FlightDetails
.Query()
.Join
(
PassengersDetails,
x => x.Flightno,
y => y.FlightNo,
(x, y) => new
{
y.PassengerId,
y.classType,
x.Flightno,
x.FlightName,
}
);
I would like to use something like..
我想使用类似..
"Above query".DefaultIfEmpty
(
new
{
y.PassengerId,
y.classType,
string.Empty,
string.Empty
}
);
FlightDetailsis Idatarepositorytype on a class and PassengerDetailsis IQueryablelocal variable result. How can I get result with PassengerIdand Classtype without flightnoand flightnameincluded in the overall results?
FlightDetails是Idatarepository类的类型，PassengerDetails是IQueryable局部变量结果。如何在PassengerId没有flightno和flightname包含在整体结果中的和 Classtype获得结果？
采纳答案by Kristof
You basically want to do a left outer join. The way you currently are using the DefaultIfEmpty method is that if the entire list is empty you provide a single default entry.
你基本上想做一个左外连接。您当前使用 DefaultIfEmpty 方法的方式是，如果整个列表为空，则您提供一个默认条目。
You should join with PassengerDetailsand for each passenger details list call the default if empty. This is the equivalent of a left outer join and it goes a little something like this:
PassengerDetails如果为空，您应该加入并为每个乘客详细信息列表调用默认值。这相当于左外连接，它有点像这样：
var data = from fd in FlightDetails
join pd in PassengersDetails on fd.Flightno equals pd.FlightNo into joinedT
from pd in joinedT.DefaultIfEmpty()
select new {
nr = fd.Flightno,
name = fd.FlightName,
passengerId = pd == null ? String.Empty : pd.PassengerId,
passengerType = pd == null ? String.Empty : pd.PassengerType
}
