Linq完全外连接[重复]答案

【问题标题】：Linq Full outer join [duplicate]Linq完全外连接[重复]
【发布时间】：2017-06-10 15:16:42
【问题描述】：

大家好，我正在尝试从 2 个表中获取完整的外部联接

前：

Table_A 
--------
_a
_c

Table_B
------
_a
_b

结果应该是

Table_C
-------
_a
_b
_c

但我似乎没有得到实际结果

这就是我所做的

IEnumerable<string> leftOuter1 = (from watcher in _watchers
                                     join attendee in attendees on watcher equals attendee into set
                                     from attendee in set.DefaultIfEmpty()
                                     select attendee);

    IEnumerable<string> rightOuter1 = (from attendee in attendees
                                       join watcher in _watchers on attendee equals watcher into set
                                      from watcher in set.DefaultIfEmpty()
                                      select watcher);


    IEnumerable<string> participants1 = leftOuter.Union(rightOuter);

在 _watchers 中，我的值为“_a”。

在与会者中，值为“_a”和“_b”。

第一个结果是_a，但第二个结果是_a，null。我在这里做错了什么？

谢谢

【问题讨论】：

标签： c# entity-framework linq linq-to-sql

【解决方案1】：

你可以看到这个

var firstNames = new[]    {
new { ID = 1, Name = "John" },
new { ID = 2, Name = "Sue" },    };

var lastNames = new[]
{
new { ID = 1, Name = "Doe" },
new { ID = 3, Name = "Smith" },
};
var leftOuterJoin = from first in firstNames
                join last in lastNames
                on first.ID equals last.ID
                into temp
                from last in temp.DefaultIfEmpty(new { first.ID, Name =       default(string) })
                select new
                {
                    first.ID,
                    FirstName = first.Name,
                    LastName = last.Name,
                };
var rightOuterJoin = from last in lastNames
                 join first in firstNames
                 on last.ID equals first.ID
                 into temp
                 from first in temp.DefaultIfEmpty(new { last.ID, Name =     default(string) })
                 select new
                 {
                     last.ID,
                     FirstName = first.Name,
                     LastName = last.Name,
                 }; var fullOuterJoin = leftOuterJoin.Union(rightOuterJoin);

见LINQ - Full Outer Join

【讨论】：