LINQ，EF联合查询join

public object GetListAdmin()

{

//return db_C56.Admins

// .Where(a => a.Status != "D").ToList();

var query1 = db_C56.Admins.Join(db_C56.Area, a => a.AreaID, ar => ar.ID, (a, ar) => new

{

userName = a.UserName,

pwd = a.Password,

dName = a.DisplayName,

areaId = a.AreaID,

hasNode = a.HasNode,

roleName = a.RoleName,

status = a.Status,

areaName = ar.Name

});

var query = from a in db_C56.Admins

join ar in db_C56.Area

on a.AreaID equals ar.ID

where a.Status != "D"

select new

{

userName = a.UserName,

pwd = a.Password,

dName = a.DisplayName,

areaId = a.AreaID,

hasNode = a.HasNode,

roleName = a.RoleName,

status = a.Status,

areaName = ar.Name

};

return query.ToList().Select(C => new Admin

{

UserName = C.userName,

Password = C.pwd,

DisplayName = C.dName,

AreaID = C.areaId,

AreaPath = C.areaName,

HasNode = C.hasNode,

RoleName = C.roleName,

Status = C.status,

});

}

[html] view plain copy







from v in Pdt_Versions

join t in Tb_TypeDics

on v.TypeName equals t.TypeName into ignored

from i in ignored.DefaultIfEmpty()

where v.Status != "D"

select new

{

ID = v.ID,

VersionName = v.VersionName,

VersionCode = v.VersionCode,

DownloadName = v.DownloadName,

DownloadURL = v.DownloadURL,

VType = v.VType,

TypeName = v.TypeName,

DisplyTypeName = i.DisplyTypeName,

}

Linq 多层嵌套查询

[csharp] view plain copy







var query1 = from p in dbContent.PostService

where p.post_type == "product" &&

(from ot1 in dbContent.OrderItemmetaService

where

(from ot2 in dbContent.OrderItemsService

where ot2.order_item_type == "line_item" &&

(from p1 in dbContent.PostService

where p1.post_type == "shop_order" && p1.post_author == userid && p1.post_status == "wc-completed"

select p1.ID).Contains(ot2.order_id)

select ot2.order_item_id).Contains(ot1.meta_id)

select ot1.meta_value).Contains(p.ID)

select new

{

id = p.ID,

name = p.post_title

};

var query2 = dbContent.PostService.Where(p =>

p.post_type == "product" &&

(dbContent.OrderItemmetaService.Where(ot1 =>

(dbContent.OrderItemsService.Where(ot2 =>

ot2.order_item_type == "line_item" && (dbContent.PostService.Where(p1 =>

p1.post_type == "shop_order" && p1.post_author == userid && p1.post_status == "wc-completed").Select(p1 => p1.ID).Contains(ot2.order_item_id))

).Select(ot2 => ot2.order_item_id).Contains(ot1.meta_id))

).Select(ot1 => ot1.meta_value).Contains(p.ID))

).Select(p => new

{

id = p.ID,

name = p.post_title

}).ToList();

Left Join 查询

from d in Doctors
join c in (
(from t in Commentaries where t.State != 'D' group t by new { t.DoctorID } into g
select new {
DoctorID = (Int64?)g.Key.DoctorID,
Total = (Int32?)g.Sum(p => p.Rating),
Evaluate = (System.Double?)g.Average(p => p.Rating)
})) on new { UserID = d.UserID } equals new { UserID = (Int64)c.DoctorID }into a_join
from p in a_join.DefaultIfEmpty()
select new {
d.ID,
UserID = (Int64?)d.UserID,
d.Name,
Evaluate = ((int?)p.Evaluate ?? (int?)0)
}

Lambda表达式

Doctors
.GroupJoin (
Commentaries
.Where (t => ((Int32)(t.State) != 68))
.GroupBy (
t =>
new
{
DoctorID = t.DoctorID
}
)
.Select (
g =>
new
{
DoctorID = (Int64?)(g.Key.DoctorID),
Total = (Int32?)(g.Sum (p => p.Rating)),
Evaluate = (Double?)(g.Average (p => p.Rating))
}
),
d =>
new
{
UserID = d.UserID
},
c =>
new
{
UserID = (Int64)(c.DoctorID)
},
(d, a_join) =>
new
{
d = d,
a_join = a_join
}
)
.SelectMany (
temp0 => temp0.a_join.DefaultIfEmpty (),
(temp0, p) =>
new
{
ID = temp0.d.ID,
UserID = (Int64?)(temp0.d.UserID),
Name = temp0.d.Name,
Evaluate = ((Int32?)(p.Evaluate) ?? (Int32?)0)
}
)

======================================================================

多个left join

from d in Doctors
join f in Functions on new { FunctionID = d.FunctionID } equals new { FunctionID = f.ID } into b_join
from f in b_join.DefaultIfEmpty()
join c in (
(from t in Commentaries where t.State != 'D' group t by new {t.DoctorID } into g
select new {
DoctorID = (Int64?)g.Key.DoctorID,
Total = (Int32?)g.Sum(p => p.Rating),
Evaluate = (System.Double?)g.Average(p => p.Rating)
})) on new { UserID = d.UserID } equals new { UserID = (Int64)c.DoctorID } into a_join
from c in a_join.DefaultIfEmpty()
select new {
d.ID,
UserID = (Int64?)d.UserID,
d.AvatarPic,
d.Name,
f.Title,
f.ContentDescribe,
Evaluate = ((int?)c.Evaluate ?? (int?)0)
}

Lambda表达式

Doctors
.GroupJoin (
Functions,
d =>
new
{
FunctionID = d.FunctionID
},
f =>
new
{
FunctionID = f.ID
},
(d, b_join) =>
new
{
d = d,
b_join = b_join
}
)
.SelectMany (
temp0 => temp0.b_join.DefaultIfEmpty (),
(temp0, f) =>
new
{
temp0 = temp0,
f = f
}
)
.GroupJoin (
Commentaries
.Where (t => ((Int32)(t.State) != 68))
.GroupBy (
t =>
new
{
DoctorID = t.DoctorID
}
)
.Select (
g =>
new
{
DoctorID = (Int64?)(g.Key.DoctorID),
Total = (Int32?)(g.Sum (p => p.Rating)),
Evaluate = (Double?)(g.Average (p => p.Rating))
}
),
temp1 =>
new
{
UserID = temp1.temp0.d.UserID
},
c =>
new
{
UserID = (Int64)(c.DoctorID)
},
(temp1, a_join) =>
new
{
temp1 = temp1,
a_join = a_join
}
)
.SelectMany (
temp2 => temp2.a_join.DefaultIfEmpty (),
(temp2, c) =>
new
{
ID = temp2.temp1.temp0.d.ID,
UserID = (Int64?)(temp2.temp1.temp0.d.UserID),
AvatarPic = temp2.temp1.temp0.d.AvatarPic,
Name = temp2.temp1.temp0.d.Name,
Title = temp2.temp1.f.Title,
ContentDescribe = temp2.temp1.f.ContentDescribe,
Evaluate = ((Int32?)(c.Evaluate) ?? (Int32?)0)
}
)