<s>
Entity	B-Application
Framework	I-Application
(	O
EF	O
)	O
is	O
an	O
open	O
source	O
object	B-General_Concept
–	I-General_Concept
relational	I-General_Concept
mapping	I-General_Concept
(	O
ORM	O
)	O
framework	O
for	O
ADO.NET	B-Device
.	O
</s>
<s>
It	O
was	O
originally	O
shipped	O
as	O
an	O
integral	O
part	O
of	O
.NET	B-Application
Framework	I-Application
,	O
however	O
starting	O
with	O
Entity	B-Application
Framework	I-Application
version	O
6.0	O
it	O
has	O
been	O
delivered	O
separately	O
from	O
the	O
.NET	B-Application
Framework	I-Application
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
6.4	O
was	O
the	O
latest	O
release	O
of	O
the	O
classic	O
framework	O
.	O
</s>
<s>
Although	O
Entity	B-Application
Framework	I-Application
6	O
is	O
still	O
supported	O
,	O
it	O
is	O
no	O
longer	O
being	O
developed	O
and	O
will	O
only	O
receive	O
fixes	O
for	O
security	O
issues	O
.	O
</s>
<s>
A	O
new	O
framework	O
known	O
as	O
Entity	B-Application
Framework	I-Application
Core	I-Application
(	O
EF	B-Application
Core	I-Application
)	O
was	O
introduced	O
in	O
2016	O
with	O
similar	O
but	O
not	O
complete	O
feature	O
parity	O
.	O
</s>
<s>
Version	O
numbering	O
of	O
this	O
framework	O
restarted	O
from	O
1.0	O
and	O
the	O
latest	O
version	O
of	O
EF	B-Application
Core	I-Application
is	O
7.0	O
.	O
</s>
<s>
The	O
Entity	B-Application
Framework	I-Application
is	O
a	O
set	O
of	O
technologies	O
in	O
ADO.NET	B-Device
that	O
supports	O
the	O
development	O
of	O
data-oriented	O
software	O
applications	O
.	O
</s>
<s>
This	O
problem	O
is	O
generally	O
referred	O
to	O
as	O
the	O
"	O
object	B-Architecture
–	I-Architecture
relational	I-Architecture
impedance	I-Architecture
mismatch	I-Architecture
"	O
.	O
</s>
<s>
Many	O
object	B-General_Concept
–	I-General_Concept
relational	I-General_Concept
mapping	I-General_Concept
(	O
ORM	O
)	O
tools	O
(	O
aka	O
"	O
object	O
–	O
relational	O
managers	O
"	O
)	O
have	O
been	O
developed	O
to	O
enable	O
developers	O
to	O
work	O
with	O
data	O
in	O
the	O
form	O
of	O
domain-specific	O
objects	B-Language
and	O
properties	O
,	O
such	O
as	O
customers	O
and	O
customer	O
addresses	O
,	O
without	O
having	O
to	O
concern	O
themselves	O
with	O
the	O
underlying	O
database	O
tables	O
and	O
columns	O
where	O
this	O
data	O
is	O
stored	O
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
is	O
the	O
ORM	O
solution	O
currently	O
promoted	O
for	O
use	O
within	O
the	O
Microsoft	O
development	O
stack	O
.	O
</s>
<s>
The	O
first	O
version	O
of	O
Entity	B-Application
Framework	I-Application
(	O
EFv1	O
)	O
was	O
included	O
with	O
.NET	B-Application
Framework	I-Application
3.5	O
Service	O
Pack	O
1	O
and	O
Visual	B-Application
Studio	I-Application
2008	I-Application
Service	O
Pack	O
1	O
,	O
released	O
on	O
.	O
</s>
<s>
The	O
second	O
version	O
of	O
Entity	B-Application
Framework	I-Application
,	O
named	O
Entity	B-Application
Framework	I-Application
4.0	O
(	O
EFv4	O
)	O
,	O
was	O
released	O
as	O
part	O
of	O
.NET	B-Application
4.0	O
on	O
12	O
April	O
2010	O
and	O
addressed	O
many	O
of	O
the	O
criticisms	O
made	O
of	O
version	O
1	O
.	O
</s>
<s>
A	O
third	O
version	O
of	O
Entity	B-Application
Framework	I-Application
,	O
version	O
4.1	O
,	O
was	O
released	O
on	O
April	O
12	O
,	O
2011	O
,	O
with	O
Code	O
First	O
support	O
.	O
</s>
<s>
A	O
refresh	O
of	O
version	O
4.1	O
,	O
named	O
Entity	B-Application
Framework	I-Application
4.1	O
Update	O
1	O
,	O
was	O
released	O
on	O
July	O
25	O
,	O
2011	O
.	O
</s>
<s>
Version	O
5.0.0	O
was	O
released	O
on	O
August	O
11	O
,	O
2012	O
and	O
is	O
targeted	O
at	O
.NET	B-Application
framework	I-Application
4.5	O
.	O
</s>
<s>
Also	O
,	O
this	O
version	O
is	O
available	O
for	O
.Net	B-Application
framework	I-Application
4	O
,	O
but	O
without	O
any	O
runtime	O
advantages	O
over	O
version	O
4	O
.	O
</s>
<s>
Version	O
6.0	O
was	O
released	O
on	O
October	O
17	O
,	O
2013	O
and	O
is	O
now	O
an	O
open	O
source	O
project	O
licensed	O
under	O
Apache	B-Application
License	I-Application
v2	O
.	O
</s>
<s>
Like	O
ASP.NET	B-Language
MVC	I-Language
,	O
its	O
source	O
code	O
is	O
hosted	O
at	O
GitHub	B-Application
using	O
Git	O
.	O
</s>
<s>
Microsoft	O
then	O
decided	O
to	O
modernize	O
,	O
componentize	O
and	O
bring	O
.NET	B-Application
cross-platform	O
to	O
Linux	O
,	O
OSX	O
and	O
elsewhere	O
,	O
meaning	O
the	O
next	O
version	O
of	O
Entity	B-Application
Framework	I-Application
would	O
be	O
a	O
complete	O
rewrite	O
.	O
</s>
<s>
On	O
27	O
June	O
2016	O
this	O
was	O
released	O
as	O
Entity	B-Application
Framework	I-Application
Core	I-Application
1.0	O
,	O
alongside	O
ASP.NET	O
Core	O
1.0	O
and	O
.NET	B-Application
Core	I-Application
1.0	I-Application
.	O
</s>
<s>
It	O
was	O
originally	O
named	O
Entity	B-Application
Framework	I-Application
7	O
,	O
but	O
was	O
renamed	O
to	O
highlight	O
that	O
it	O
was	O
a	O
complete	O
rewrite	O
rather	O
than	O
an	O
incremental	O
upgrade	O
and	O
it	O
does	O
n't	O
replace	O
EF6	O
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Core	I-Application
1.0	O
is	O
licensed	O
under	O
Apache	B-Application
License	I-Application
v2	O
,	O
and	O
was	O
built	O
entirely	O
in	O
the	O
open	O
on	O
.	O
</s>
<s>
While	O
Entity	B-Application
Framework	I-Application
Core	I-Application
1.0	O
shares	O
some	O
conceptual	O
similarities	O
with	O
prior	O
versions	O
of	O
Entity	B-Application
Framework	I-Application
,	O
it	O
was	O
a	O
completely	O
new	O
codebase	O
designed	O
to	O
be	O
more	O
efficient	O
,	O
powerful	O
,	O
flexible	O
,	O
and	O
extensible	O
,	O
running	O
on	O
Windows	O
,	O
Linux	O
and	O
OSX	O
,	O
and	O
supporting	O
a	O
new	O
range	O
of	O
relational	O
and	O
NoSQL	B-General_Concept
data	O
stores	O
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Core	I-Application
3.0	O
was	O
released	O
on	O
along	O
with	O
Visual	B-Application
Studio	I-Application
2019	O
16.3	O
and	O
ASP.NET	O
Core	O
3.0	O
,	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Core	I-Application
3.1	O
(	O
EF	B-Application
Core	I-Application
3.1	O
)	O
was	O
formally	O
released	O
for	O
production	O
use	O
on	O
and	O
will	O
be	O
the	O
preferred	O
long-term	O
supported	O
version	O
until	O
at	O
least	O
3	O
December	O
2022	O
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Core	I-Application
5.0	O
(	O
EF	B-Application
Core	I-Application
5	O
)	O
was	O
released	O
for	O
production	O
use	O
on	O
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Core	I-Application
6.0	O
(	O
EF	B-Application
Core	I-Application
6	O
)	O
was	O
released	O
on	O
and	O
will	O
be	O
the	O
preferred	O
long-term	O
supported	O
version	O
until	O
at	O
least	O
12	O
November	O
2024	O
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Core	I-Application
7.0	O
(	O
EF	B-Application
Core	I-Application
7	O
)	O
was	O
released	O
on	O
adding	O
features	O
such	O
as	O
and	O
.	O
</s>
<s>
The	O
architecture	O
of	O
the	O
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
,	O
from	O
the	O
bottom	O
up	O
,	O
consists	O
of	O
the	O
following	O
:	O
</s>
<s>
Data	O
source	O
specific	O
providers	O
,	O
which	O
abstract	O
the	O
ADO.NET	B-Device
interfaces	O
to	O
connect	O
to	O
the	O
database	O
when	O
programming	O
against	O
the	O
conceptual	O
schema	O
.	O
</s>
<s>
Map	O
provider	O
,	O
a	O
database-specific	O
provider	O
that	O
translates	O
the	O
Entity	O
SQL	B-Language
command	O
tree	O
into	O
a	O
query	B-Language
in	O
the	O
native	O
SQL	B-Language
flavor	O
of	O
the	O
database	O
.	O
</s>
<s>
Query	B-Language
and	O
update	O
pipeline	O
,	O
processes	O
queries	B-Language
,	O
filters	O
and	O
updates	O
requests	O
to	O
convert	O
them	O
into	O
canonical	O
command	O
trees	O
which	O
are	O
then	O
converted	O
into	O
store-specific	O
queries	B-Language
by	O
the	O
map	O
provider	O
.	O
</s>
<s>
It	O
follows	O
the	O
ADO.NET	B-Device
pattern	O
of	O
using	O
Connection	O
objects	B-Language
to	O
refer	O
to	O
the	O
map	O
provider	O
,	O
using	O
Command	O
objects	B-Language
to	O
send	O
the	O
query	B-Language
,	O
and	O
returning	O
EntityResultSets	O
or	O
EntitySets	O
containing	O
the	O
result	O
.	O
</s>
<s>
Disconnected	O
components	O
,	O
which	O
locally	O
cache	O
datasets	O
and	O
entity	O
sets	O
for	O
using	O
the	O
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
in	O
an	O
occasionally	O
connected	O
environment	O
.	O
</s>
<s>
Embedded	O
database	O
:	O
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
includes	O
a	O
lightweight	O
embedded	O
database	O
for	O
client-side	O
caching	O
and	O
querying	O
of	O
relational	O
data	O
.	O
</s>
<s>
Design	O
tools	O
,	O
such	O
as	O
Mapping	O
Designer	O
,	O
are	O
also	O
included	O
with	O
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
,	O
which	O
simplifies	O
the	O
job	O
of	O
mapping	O
a	O
conceptual	O
schema	O
to	O
the	O
relational	O
schema	O
and	O
specifying	O
which	O
properties	O
of	O
an	O
entity	O
type	O
correspond	O
to	O
which	O
table	O
in	O
the	O
database	O
.	O
</s>
<s>
Object	O
services	O
,	O
automatically	O
generate	O
code	O
for	O
CLR	O
classes	O
that	O
expose	O
the	O
same	O
properties	O
as	O
an	O
entity	O
,	O
thus	O
enabling	O
instantiation	O
of	O
entities	O
as	O
.NET	B-Application
objects	B-Language
.	O
</s>
<s>
The	O
Entity	O
Data	O
Model	O
(	O
EDM	O
)	O
specifies	O
the	O
conceptual	O
model	O
(	O
CSDL	O
)	O
of	O
the	O
data	O
,	O
using	O
a	O
modelling	O
technique	O
that	O
is	O
itself	O
called	O
Entity	O
Data	O
Model	O
,	O
an	O
extended	O
version	O
of	O
the	O
entity	B-Architecture
–	I-Architecture
relationship	I-Architecture
model	I-Architecture
.	O
</s>
<s>
Visual	B-Application
Studio	I-Application
also	O
provides	O
the	O
Entity	O
Designer	O
for	O
visual	O
creation	O
of	O
the	O
EDM	O
and	O
the	O
mapping	O
specification	O
.	O
</s>
<s>
Entity	O
Data	O
Model	O
Wizard	O
in	O
Visual	B-Application
Studio	I-Application
initially	O
generates	O
a	O
one-to-one	O
(	O
1:1	O
)	O
mapping	O
between	O
the	O
database	O
schema	O
and	O
the	O
conceptual	O
schema	O
in	O
most	O
of	O
the	O
cases	O
.	O
</s>
<s>
Entity	O
Types	O
form	O
the	O
class	O
of	O
objects	B-Language
entities	O
conform	O
to	O
,	O
with	O
the	O
Entities	O
being	O
instances	O
of	O
the	O
entity	O
types	O
.	O
</s>
<s>
Entities	O
represent	O
individual	O
objects	B-Language
that	O
form	O
a	O
part	O
of	O
the	O
problem	O
being	O
solved	O
by	O
the	O
application	O
and	O
are	O
indexed	O
by	O
a	O
key	O
.	O
</s>
<s>
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
uses	O
the	O
EDM	O
to	O
actually	O
perform	O
the	O
mapping	O
letting	O
the	O
application	O
work	O
with	O
the	O
entities	O
,	O
while	O
internally	O
abstracting	O
the	O
use	O
of	O
ADO.NET	B-Device
constructs	O
like	O
DataSet	O
and	O
RecordSet	O
.	O
</s>
<s>
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
performs	O
the	O
joins	B-Language
necessary	O
to	O
have	O
entity	O
reference	O
information	O
from	O
multiple	O
tables	O
,	O
or	O
when	O
a	O
relationship	O
is	O
traversed	O
.	O
</s>
<s>
When	O
an	O
entity	O
is	O
updated	O
,	O
it	O
traces	O
back	O
which	O
table	O
the	O
information	O
came	O
from	O
and	O
issues	O
SQL	B-Language
update	O
statements	O
to	O
update	O
the	O
tables	O
in	O
which	O
some	O
data	O
has	O
been	O
updated	O
.	O
</s>
<s>
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
uses	O
eSQL	O
,	O
a	O
derivative	O
of	O
SQL	B-Language
,	O
to	O
perform	O
queries	B-Language
,	O
set-theoretic	O
operations	O
,	O
and	O
updates	O
on	O
entities	O
and	O
their	O
relationships	O
.	O
</s>
<s>
Queries	B-Language
in	O
eSQL	O
,	O
if	O
required	O
,	O
are	O
then	O
translated	O
to	O
the	O
native	O
SQL	B-Language
flavor	O
of	O
the	O
underlying	O
database	O
.	O
</s>
<s>
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
includes	O
Object	O
Service	O
that	O
presents	O
these	O
entities	O
as	O
Objects	B-Language
with	O
the	O
elements	O
and	O
relationships	O
exposed	O
as	O
properties	O
.	O
</s>
<s>
Thus	O
Entity	O
objects	B-Language
are	O
just	O
front-end	O
to	O
the	O
instances	O
of	O
the	O
EDM	O
entity	O
types	O
,	O
which	O
lets	O
Object	B-Language
Oriented	I-Language
languages	I-Language
access	O
and	O
use	O
them	O
.	O
</s>
<s>
Similarly	O
,	O
other	O
front-ends	O
can	O
be	O
created	O
,	O
which	O
expose	O
the	O
entities	O
via	O
web	O
services	O
(	O
e.g.	O
,	O
WCF	B-Device
Data	I-Device
Services	I-Device
)	O
or	O
XML	O
that	O
is	O
used	O
when	O
entities	O
are	O
serialized	O
for	O
persistence	O
storage	O
or	O
over-the-wire	O
transfer	O
.	O
</s>
<s>
Entities**	O
are	O
instances	O
of	O
EntityTypes	O
;	O
they	O
represent	O
the	O
individual	O
instances	O
of	O
the	O
objects	B-Language
(	O
such	O
as	O
customer	O
,	O
orders	O
)	O
to	O
which	O
the	O
information	O
pertains	O
.	O
</s>
<s>
The	O
properties	O
of	O
an	O
entity	O
type	O
in	O
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
are	O
fully	O
typed	O
,	O
and	O
are	O
fully	O
compatible	O
with	O
the	O
type	O
system	O
used	O
in	O
a	O
DBMS	O
system	O
,	O
as	O
well	O
as	O
the	O
Common	O
Type	O
System	O
of	O
the	O
.NET	B-Application
Framework	I-Application
.	O
</s>
<s>
In	O
Entity	B-Application
Framework	I-Application
v1	O
ComplexTypes	O
cannot	O
be	O
inherited	O
.	O
</s>
<s>
However	O
,	O
in	O
the	O
initial	O
release	O
of	O
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
,	O
relationships	O
are	O
limited	O
to	O
a	O
binary	O
(	O
of	O
degree	O
two	O
)	O
bi-directional	O
relationship	O
.	O
</s>
<s>
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
uses	O
an	O
XML	O
based	O
Data	O
Definition	O
Language	O
called	O
Schema	O
Definition	O
Language	O
(	O
SDL	O
)	O
to	O
define	O
the	O
EDM	O
Schema	O
.	O
</s>
<s>
ADO.NET	B-Application
Entity	I-Application
Framework	I-Application
uses	O
a	O
variant	O
of	O
the	O
Structured	B-Language
Query	I-Language
Language	I-Language
,	O
named	O
Entity	O
SQL	B-Language
,	O
which	O
is	O
aimed	O
at	O
writing	O
declarative	O
queries	B-Language
and	O
updates	O
over	O
entities	O
and	O
entity	B-Architecture
relationships	I-Architecture
–	O
at	O
the	O
conceptual	O
level	O
.	O
</s>
<s>
It	O
differs	O
from	O
SQL	B-Language
in	O
that	O
it	O
does	O
not	O
have	O
explicit	O
constructs	O
for	O
joins	B-Language
because	O
the	O
EDM	O
is	O
designed	O
to	O
abstract	O
partitioning	O
data	O
across	O
tables	O
.	O
</s>
<s>
Querying	O
against	O
the	O
conceptual	O
model	O
is	O
facilitated	O
by	O
EntityClient	O
classes	O
,	O
which	O
accepts	O
an	O
Entity	O
SQL	B-Language
query	B-Language
.	O
</s>
<s>
The	O
query	B-Language
pipeline	O
parses	O
the	O
Entity	O
SQL	B-Language
query	B-Language
into	O
a	O
command	O
tree	O
,	O
segregating	O
the	O
query	B-Language
across	O
multiple	O
tables	O
,	O
which	O
is	O
handed	O
over	O
to	O
the	O
EntityClient	O
provider	O
.	O
</s>
<s>
Like	O
ADO.NET	B-Device
data	I-Device
providers	I-Device
,	O
an	O
EntityClient	O
provider	O
is	O
also	O
initialized	O
using	O
a	O
Connection	O
object	O
,	O
which	O
in	O
addition	O
to	O
the	O
usual	O
parameters	O
of	O
data	O
store	O
and	O
authentication	O
info	O
,	O
requires	O
the	O
SDL	O
schema	O
and	O
the	O
mapping	O
information	O
.	O
</s>
<s>
The	O
EntityClient	O
provider	O
in	O
turn	O
then	O
turns	O
the	O
Entity	O
SQL	B-Language
command	O
tree	O
into	O
an	O
SQL	B-Language
query	B-Language
in	O
the	O
native	O
flavor	O
of	O
the	O
database	O
.	O
</s>
<s>
The	O
execution	O
of	O
the	O
query	B-Language
then	O
returns	O
an	O
Entity	O
SQL	B-Language
ResultSet	O
,	O
which	O
is	O
not	O
limited	O
to	O
a	O
tabular	O
structure	O
,	O
unlike	O
ADO.NET	B-Device
ResultSets	O
.	O
</s>
<s>
Entity	O
SQL	B-Language
enhances	O
SQL	B-Language
by	O
adding	O
intrinsic	O
support	O
for	O
:	O
</s>
<s>
Types	O
,	O
as	O
ADO.NET	B-Device
entities	O
are	O
fully	O
typed	O
.	O
</s>
<s>
Canonical	O
functions	O
are	O
supported	O
by	O
all	O
Entity	B-Application
Framework	I-Application
compliant	O
data	O
providers	O
.	O
</s>
<s>
They	O
can	O
be	O
used	O
in	O
an	O
Entity	O
SQL	B-Language
query	B-Language
.	O
</s>
<s>
Also	O
,	O
most	O
of	O
the	O
extension	O
methods	O
in	O
LINQ	B-Language
to	O
Entities	O
are	O
translated	O
to	O
canonical	O
functions	O
.	O
</s>
<s>
When	O
ADO.NET	B-Device
data	I-Device
provider	I-Device
receives	O
a	O
function	O
,	O
it	O
translates	O
it	O
to	O
the	O
desired	O
SQL	B-Language
statement	O
.	O
</s>
<s>
The	O
LINQ	B-Language
to	O
Entities	O
provider	O
allows	O
LINQ	B-Language
to	O
be	O
used	O
to	O
query	B-Language
various	O
RDBMS	O
data	O
sources	O
.	O
</s>
<s>
Several	O
database	O
server	O
specific	O
providers	O
with	O
Entity	B-Application
Framework	I-Application
support	O
are	O
available	O
.	O
</s>
<s>
In	O
the	O
Entity	B-Application
Framework	I-Application
v4	O
new	O
methods	O
ExecuteStoreQuery( )	O
and	O
ExecuteStoreCommand( )	O
were	O
added	O
to	O
the	O
class	O
ObjectContext	O
.	O
</s>
<s>
Visual	B-Application
Studio	I-Application
has	O
a	O
feature	O
called	O
Visualizer	O
.	O
</s>
<s>
A	O
LINQ	B-Language
query	B-Language
written	O
in	O
Visual	B-Application
Studio	I-Application
can	O
be	O
viewed	O
as	O
Native	O
SQL	B-Language
using	O
a	O
Visualizer	O
during	O
debug	O
session	O
.	O
</s>
<s>
A	O
Visualizer	O
for	O
LINQ	B-Language
to	O
Entities	O
(	O
Object	O
Query	B-Language
)	O
targeting	O
all	O
RDBMS	O
is	O
available	O
in	O
the	O
Visual	B-Application
Studio	I-Application
Marketplace	O
.	O
</s>
<s>
Various	O
profilers	O
are	O
commercially	O
available	O
to	O
troubleshoot	O
performance	O
issues	O
using	O
Entity	B-Application
Framework	I-Application
,	O
both	O
for	O
EF	O
and	O
EF	B-Application
Core	I-Application
variants	O
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Core	I-Application
Tools	O
and	O
Extensions	O
are	O
available	O
to	O
enhance	O
the	O
performance	O
of	O
Entity	B-Application
Framework	I-Application
Core	I-Application
.	O
</s>
<s>
Entity	B-Application
Framework	I-Application
Tools	O
and	O
Extensions	O
are	O
available	O
to	O
enhance	O
the	O
performance	O
of	O
Entity	B-Application
Framework	I-Application
.	O
</s>
