linq的 full join 怎么写

发布网友发布时间：2022-04-26 01:59

共1个回答

热心网友时间：2022-06-19 19:26

Linq to Sql:
var a=from g in Groups
join u in Users
on g.Id equals u.GroupId
into Grp
from grp in Grp.DefaultIfEmpty()
select new { GroupName=g.GroupName, UserName=(grp==null)?"":grp.UserName};

var b=from u in Users
join g in Groups
on u.GroupId equals g.Id
into Grp
from grp in Grp.DefaultIfEmpty()
select new { GroupName=(grp==null)?"":grp.GroupName, UserName=u.UserName};

var c=a.Concat(b).Distinct();
c.Dump();

Lambda:
Groups
.GroupJoin (
Users,
g => (Int32?)(g.Id),
u => u.GroupId,
(g, Grp) =>
new
{
g = g,
Grp = Grp
}
)
.SelectMany (
temp0 => temp0.Grp.DefaultIfEmpty (),
(temp0, grp) =>
new
{
GroupName = temp0.g.GroupName,
UserName = (grp == null) ? "" : grp.UserName
}
)
.Concat (
Users
.GroupJoin (
Groups,
u => u.GroupId,
g => (Int32?)(g.Id),
(u, Grp) =>
new
{
u = u,
Grp = Grp
}
)
.SelectMany (
temp2 => temp2.Grp.DefaultIfEmpty (),
(temp2, grp) =>
new
{
GroupName = (grp == null) ? "" : grp.GroupName,
UserName = temp2.u.UserName
}
)
)
.Distinct ()