我有两个名为 CountryMobility 的对象,我相信我需要将它们与完整的外部联接结合起来。我如何使用 linq 来做到这一点?
public class CountryMobility
{
public string countryCode { get; set; }
public int inbound { get; set; }
public int outbound { get; set; }
}
我想像这样组合其中两个对象:
inboundStudents:
countryCode | inbound | outbound
EG | 2 | 0
CA | 3 | 0
CH | 5 | 0
outboundStudents:
countryCode | inbound | outbound
PE | 0 | 1
CA | 0 | 4
CH | 0 | 5
-
-
-
-
V
combinedStudents:
countryCode | inbound | outbound
PE | 0 | 1
CA | 3 | 4
CH | 5 | 5
EG | 2 | 0
我尝试了以下 linq 语句,但无法找出正确的语法。我目前在附近遇到语法错误 两个语句中都有 temp.DefaultIfEmpty(new { first.ID, inbound = 0, outbound=0 }) 。
var leftOuterJoin =
from first in inboundActivities
join last in outboundActivities
on first.countryCode equals last.countryCode
into temp
from last in temp.DefaultIfEmpty
(new { first.countryCode, inbound = 0, outbound=0 })
select new CountryMobility
{
countryCode = first.countryCode,
inbound = first.inbound,
outbound = last.outbound,
};
var rightOuterJoin =
from last in outboundActivities
join first in inboundActivities
on last.countryCode equals first.countryCode
into temp
from first in temp.DefaultIfEmpty
(new { last.countryCode, inbound = 0, outbound = 0 })
select new CountryMobility
{
countryCode = last.countryCode,
inbound = first.inbound,
outbound = last.outbound,
};
var fullOuterJoin = leftOuterJoin.Union(rightOuterJoin);
最佳答案
在您的最新信息之后。在我看来,你可以做一些更简单的事情。即随后按国家/地区代码分组的 UNION ALL
。
可以使用 Concat
方法创建 UNION ALL
。
下面的示例对我有用(在内存集合中使用)。该查询显示在 Run
方法中。
public class CountryMobility
{
public string countryCode { get; set; }
public int inbound { get; set; }
public int outbound { get; set; }
}
public static class JoinedMobilityQuery
{
static CountryMobility[] inbound = {
new CountryMobility() { countryCode = "EG", inbound = 2 },
new CountryMobility() { countryCode = "CA", inbound = 3 },
new CountryMobility() { countryCode = "CH", inbound = 5 },
};
static CountryMobility[] outbound = {
new CountryMobility() { countryCode = "PE", outbound = 1 },
new CountryMobility() { countryCode = "CA", outbound = 4 },
new CountryMobility() { countryCode = "CH", outbound = 6 },
};
static IQueryable<CountryMobility> Inbound()
{
return inbound.AsQueryable();
}
static IQueryable<CountryMobility> Outbound()
{
return outbound.AsQueryable();
}
public static void Run()
{
var transfers = from t in Inbound().Concat(Outbound())
group t by t.countryCode into g
select new CountryMobility() {
countryCode = g.Key,
inbound = g.Sum(x => x.inbound),
outbound = g.Sum(x => x.outbound),
};
foreach (var transfer in transfers)
Console.WriteLine("{0}\t{1}\t{2}", transfer.countryCode, transfer.inbound, transfer.outbound);
}
}
关于c# - 两个对象上的 Linq 完全外连接,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/29690084/