C# LINQ 查询中的左外连接
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Left outer join in LINQ query
提问by nsutgio
Possible Duplicate:
LEFT OUTER JOIN in LINQ
可能的重复：
LINQ 中的 LEFT OUTER JOIN
How to make LINQ query with left outer joins?
如何使用左外连接进行 LINQ 查询？
采纳答案by Habib
You can use Enumerable.DefaultIfEmptyMethod for left outer join.
您可以使用Enumerable.DefaultIfEmpty方法进行左外连接。
You may see: How to: Perform Left Outer Joins (C# Programming Guide) - MSDN
您可能会看到：如何：执行左外连接（C# 编程指南）- MSDN
Consider the following example from MSDN,
考虑以下来自 MSDN 的示例，
class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
class Pet
{
public string Name { get; set; }
public Person Owner { get; set; }
}
Left outer join query can be:
左外连接查询可以是：
var query = from person in people
join pet in pets on person equals pet.Owner into gj
from subpet in gj.DefaultIfEmpty()
select new { person.FirstName, PetName = (subpet == null ? String.Empty : subpet.Name) };
回答by Felix
var query = (from t1 in Context.Table1
join t2temp in Context.Table2 on t1.Id equals t2.Id into tempJoin
from t2 in tempJoin.DefaultIfEmpty()
select ...);
