<s>
C#	O
(	O
pronounced	O
)	O
is	O
a	O
general-purpose	O
high-level	B-Language
programming	I-Language
language	I-Language
supporting	O
multiple	O
paradigms	O
.	O
</s>
<s>
C#	O
encompasses	O
static	O
typing	O
,	O
strong	O
typing	O
,	O
lexically	O
scoped	O
,	O
imperative	B-Application
,	O
declarative	B-Language
,	O
functional	B-Language
,	O
generic	B-Language
,	O
object-oriented	B-Language
(	O
class-based	O
)	O
,	O
and	O
component-oriented	B-Architecture
programming	I-Architecture
disciplines	O
.	O
</s>
<s>
The	O
C#	O
programming	O
language	O
was	O
designed	O
by	O
Anders	O
Hejlsberg	O
from	O
Microsoft	O
in	O
2000	O
and	O
was	O
later	O
approved	O
as	O
an	O
international	O
standard	O
by	O
Ecma	O
(	O
ECMA-334	B-Application
)	O
in	O
2002	O
and	O
ISO/IEC	O
(	O
ISO/IEC	B-Application
23270	I-Application
)	O
in	O
2003	O
.	O
</s>
<s>
Microsoft	O
introduced	O
C#	O
along	O
with	O
.NET	B-Application
Framework	I-Application
and	O
Visual	B-Application
Studio	I-Application
,	O
both	O
of	O
which	O
were	O
closed-source	B-Application
.	O
</s>
<s>
At	O
the	O
time	O
,	O
Microsoft	O
had	O
no	O
open-source	B-Application
products	O
.	O
</s>
<s>
Four	O
years	O
later	O
,	O
in	O
2004	O
,	O
a	O
free	B-License
and	I-License
open-source	I-License
project	O
called	O
Mono	B-Application
began	O
,	O
providing	O
a	O
cross-platform	B-Operating_System
compiler	B-Language
and	O
runtime	B-Device
environment	I-Device
for	O
the	O
C#	O
programming	O
language	O
.	O
</s>
<s>
A	O
decade	O
later	O
,	O
Microsoft	O
released	O
Visual	B-Language
Studio	I-Language
Code	I-Language
(	O
code	O
editor	O
)	O
,	O
Roslyn	B-Application
(	O
compiler	B-Language
)	O
,	O
and	O
the	B-Application
unified	I-Application
.NET	I-Application
platform	I-Application
(	O
software	O
framework	O
)	O
,	O
all	O
of	O
which	O
support	O
C#	O
and	O
are	O
free	O
,	O
open-source	B-Application
,	O
and	O
cross-platform	B-Operating_System
.	O
</s>
<s>
Mono	B-Application
also	O
joined	O
Microsoft	O
but	O
was	O
not	O
merged	O
into	O
.NET	B-Application
.	O
</s>
<s>
the	O
most	O
recent	O
stable	O
version	O
of	O
the	O
language	O
is	O
C#	O
11.0	O
,	O
which	O
was	O
released	O
in	O
2022	O
in	O
.NET	O
7.0	O
.	O
</s>
<s>
The	O
Ecma	O
standard	O
lists	O
these	O
design	O
goals	O
for	O
C#	O
:	O
</s>
<s>
The	O
language	O
is	O
intended	O
to	O
be	O
a	O
simple	O
,	O
modern	O
,	O
general-purpose	O
,	O
object-oriented	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
The	O
language	O
,	O
and	O
implementations	O
thereof	O
,	O
should	O
provide	O
support	O
for	O
software	O
engineering	O
principles	O
such	O
as	O
strong	O
type	O
checking	O
,	O
array	B-Data_Structure
bounds	I-Data_Structure
checking	I-Data_Structure
,	O
detection	O
of	O
attempts	O
to	O
use	O
uninitialized	B-Error_Name
variables	I-Error_Name
,	O
and	O
automatic	B-General_Concept
garbage	I-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
Software	O
robustness	O
,	O
durability	O
,	O
and	O
programmer	B-Application
productivity	O
are	O
important	O
.	O
</s>
<s>
The	O
language	O
is	O
intended	O
for	O
use	O
in	O
developing	O
software	B-Architecture
components	I-Architecture
suitable	O
for	O
deployment	O
in	O
distributed	O
environments	O
.	O
</s>
<s>
Portability	B-Architecture
is	O
very	O
important	O
for	O
source	O
code	O
and	O
programmers	B-Application
,	O
especially	O
those	O
already	O
familiar	O
with	O
C	B-Language
and	O
C++	B-Language
.	O
</s>
<s>
Support	O
for	O
internationalization	B-General_Concept
is	O
very	O
important	O
.	O
</s>
<s>
C#	O
is	O
intended	O
to	O
be	O
suitable	O
for	O
writing	O
applications	O
for	O
both	O
hosted	O
and	O
embedded	B-Architecture
systems	I-Architecture
,	O
ranging	O
from	O
the	O
very	O
large	O
that	O
use	O
sophisticated	O
operating	B-General_Concept
systems	I-General_Concept
,	O
down	O
to	O
the	O
very	O
small	O
having	O
dedicated	O
functions	O
.	O
</s>
<s>
Although	O
C#	O
applications	O
are	O
intended	O
to	O
be	O
economical	O
with	O
regard	O
to	O
memory	O
and	O
processing	O
power	O
requirements	O
,	O
the	O
language	O
was	O
not	O
intended	O
to	O
compete	O
directly	O
on	O
performance	O
and	O
size	O
with	O
C	B-Language
or	O
assembly	O
language	O
.	O
</s>
<s>
During	O
the	O
development	O
of	O
the	O
.NET	B-Application
Framework	I-Application
,	O
the	O
class	O
libraries	B-Library
were	O
originally	O
written	O
using	O
a	O
managed	O
code	B-Language
compiler	I-Language
system	O
called	O
"	O
Simple	O
Managed	O
C	B-Language
"	O
(	O
SMC	O
)	O
.	O
</s>
<s>
In	O
January	O
1999	O
,	O
Anders	O
Hejlsberg	O
formed	O
a	O
team	O
to	O
build	O
a	O
new	O
language	O
at	O
the	O
time	O
called	O
Cool	O
,	O
which	O
stood	O
for	O
"	O
C-like	B-Language
Object	B-Language
Oriented	I-Language
Language	I-Language
"	O
.	O
</s>
<s>
By	O
the	O
time	O
the	O
.NET	B-Application
project	O
was	O
publicly	O
announced	O
at	O
the	O
July	O
2000	O
Professional	O
Developers	B-Application
Conference	O
,	O
the	O
language	O
had	O
been	O
renamed	O
C#	O
,	O
and	O
the	O
class	O
libraries	B-Library
and	O
ASP.NET	B-Application
runtime	O
had	O
been	O
ported	O
to	O
C#	O
.	O
</s>
<s>
Hejlsberg	O
is	O
C#'s	O
principal	O
designer	O
and	O
lead	O
architect	O
at	O
Microsoft	O
,	O
and	O
was	O
previously	O
involved	O
with	O
the	O
design	O
of	O
Turbo	B-Application
Pascal	I-Application
,	O
Embarcadero	B-Language
Delphi	I-Language
(	O
formerly	O
CodeGear	B-Language
Delphi	I-Language
,	O
Inprise	O
Delphi	B-Language
and	O
Borland	B-Language
Delphi	I-Language
)	O
,	O
and	O
Visual	B-Application
J++	I-Application
.	O
</s>
<s>
C++	B-Language
,	O
Java	B-Language
,	O
Delphi	B-Language
,	O
and	O
Smalltalk	B-Application
)	O
drove	O
the	O
fundamentals	O
of	O
the	O
Common	O
Language	O
Runtime	O
(	O
CLR	O
)	O
,	O
which	O
,	O
in	O
turn	O
,	O
drove	O
the	O
design	O
of	O
the	O
C#	O
language	O
itself	O
.	O
</s>
<s>
James	O
Gosling	O
,	O
who	O
created	O
the	O
Java	B-Language
programming	I-Language
language	I-Language
in	O
1994	O
,	O
and	O
Bill	O
Joy	O
,	O
a	O
co-founder	O
of	O
Sun	O
Microsystems	O
,	O
the	O
originator	O
of	O
Java	B-Language
,	O
called	O
C#	O
an	O
"	O
imitation	O
"	O
of	O
Java	B-Language
;	O
Gosling	O
further	O
said	O
that	O
"	O
[	O
C#	O
is ]	O
sort	O
of	O
Java	B-Language
with	O
reliability	O
,	O
productivity	O
and	O
security	O
deleted.	O
"	O
</s>
<s>
Klaus	O
Kreft	O
and	O
Angelika	O
Langer	O
(	O
authors	O
of	O
a	O
C++	B-Language
streams	O
book	O
)	O
stated	O
in	O
a	O
blog	O
post	O
that	O
"	O
Java	B-Language
and	O
C#	O
are	O
almost	O
identical	O
programming	O
languages	O
.	O
</s>
<s>
Boring	O
repetition	O
that	O
lacks	O
innovation	O
,	O
"	O
"	O
Hardly	O
anybody	O
will	O
claim	O
that	O
Java	B-Language
or	O
C#	O
are	O
revolutionary	O
programming	O
languages	O
that	O
changed	O
the	O
way	O
we	O
write	O
programs	O
,	O
"	O
and	O
"	O
C#	O
borrowed	O
a	O
lot	O
from	O
Java	B-Language
-	O
and	O
vice	O
versa	O
.	O
</s>
<s>
Now	O
that	O
C#	O
supports	O
boxing	O
and	O
unboxing	O
,	O
we	O
'll	O
have	O
a	O
very	O
similar	O
feature	O
in	O
Java.	O
"	O
</s>
<s>
In	O
July	O
2000	O
,	O
Hejlsberg	O
said	O
that	O
C#	O
is	O
"	O
not	O
a	O
Java	B-Language
clone	O
"	O
and	O
is	O
"	O
much	O
closer	O
to	O
C++	B-Language
"	O
in	O
its	O
design	O
.	O
</s>
<s>
Since	O
the	O
release	O
of	O
C#	B-Language
2.0	I-Language
in	O
November	O
2005	O
,	O
the	O
C#	O
and	O
Java	B-Language
languages	I-Language
have	O
evolved	O
on	O
increasingly	O
divergent	O
trajectories	O
,	O
becoming	O
two	O
quite	O
different	O
languages	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
major	O
departures	O
came	O
with	O
the	O
addition	O
of	O
generics	B-Language
to	O
both	O
languages	O
,	O
with	O
vastly	O
different	O
implementations	O
.	O
</s>
<s>
C#	O
makes	O
use	O
of	O
reification	O
to	O
provide	O
"	O
first-class	O
"	O
generic	B-Language
objects	O
that	O
can	O
be	O
used	O
like	O
any	O
other	O
class	O
,	O
with	O
code	B-Application
generation	I-Application
performed	O
at	O
class-load	O
time	O
.	O
</s>
<s>
Furthermore	O
,	O
C#	O
has	O
added	O
several	O
major	O
features	O
to	O
accommodate	O
functional-style	O
programming	O
,	O
culminating	O
in	O
the	O
LINQ	B-Language
extensions	O
released	O
with	O
C#	B-Language
3.0	I-Language
and	O
its	O
supporting	O
framework	O
of	O
lambda	B-General_Concept
expressions	I-General_Concept
,	O
extension	O
methods	O
,	O
and	O
anonymous	B-Language
types	I-Language
.	O
</s>
<s>
These	O
features	O
enable	O
C#	O
programmers	B-Application
to	O
use	O
functional	B-Language
programming	I-Language
techniques	O
,	O
such	O
as	O
closures	B-Language
,	O
when	O
it	O
is	O
advantageous	O
to	O
their	O
application	O
.	O
</s>
<s>
The	O
LINQ	B-Language
extensions	O
and	O
the	O
functional	B-Language
imports	O
help	O
developers	B-Application
reduce	O
the	O
amount	O
of	O
boilerplate	O
code	O
that	O
is	O
included	O
in	O
common	O
tasks	O
like	O
querying	O
a	O
database	O
,	O
parsing	O
an	O
xml	O
file	O
,	O
or	O
searching	O
through	O
a	O
data	O
structure	O
,	O
shifting	O
the	O
emphasis	O
onto	O
the	O
actual	O
program	O
logic	O
to	O
help	O
improve	O
readability	O
and	O
maintainability	O
.	O
</s>
<s>
C#	O
used	O
to	O
have	O
a	O
mascot	B-Application
called	O
Andy	O
(	O
named	O
after	O
Anders	O
Hejlsberg	O
)	O
.	O
</s>
<s>
C#	O
was	O
originally	O
submitted	O
to	O
the	O
ISO/IEC	O
JTC	O
1	O
subcommittee	O
SC	O
22	O
for	O
review	O
,	O
under	O
ISO/IEC	O
23270:2003	O
,	O
was	O
withdrawn	O
and	O
was	O
then	O
approved	O
under	O
ISO/IEC	O
23270:2006	O
.	O
</s>
<s>
Microsoft	O
first	O
used	O
the	O
name	O
C#	O
in	O
1988	O
for	O
a	O
variant	O
of	O
the	O
C	B-Language
language	I-Language
designed	O
for	O
incremental	O
compilation	B-Language
.	O
</s>
<s>
The	O
name	O
"	O
C	B-Application
sharp	I-Application
"	O
was	O
inspired	O
by	O
the	O
musical	O
notation	O
whereby	O
a	B-Language
sharp	I-Language
symbol	O
indicates	O
that	O
the	O
written	O
note	O
should	O
be	O
made	O
a	O
semitone	O
higher	O
in	O
pitch	O
.	O
</s>
<s>
This	O
is	O
similar	O
to	O
the	O
language	O
name	O
of	O
C++	B-Language
,	O
where	O
"	O
++	O
"	O
indicates	O
that	O
a	O
variable	O
should	O
be	O
incremented	O
by	O
1	O
after	O
being	O
evaluated	O
.	O
</s>
<s>
The	O
sharp	O
symbol	O
also	O
resembles	O
a	O
ligature	O
of	O
four	O
"	O
+	O
"	O
symbols	O
(	O
in	O
a	O
two-by-two	O
grid	O
)	O
,	O
further	O
implying	O
that	O
the	O
language	O
is	O
an	O
increment	O
of	O
C++	B-Language
.	O
</s>
<s>
This	O
convention	O
is	O
reflected	O
in	O
the	O
ECMA-334	B-Application
C#	O
Language	O
Specification	O
.	O
</s>
<s>
The	O
"	O
sharp	O
"	O
suffix	O
has	O
been	O
used	O
by	O
a	O
number	O
of	O
other	O
.NET	B-Application
languages	O
that	O
are	O
variants	O
of	O
existing	O
languages	O
,	O
including	O
J#	B-Language
(	O
a	O
.NET	B-Application
language	O
also	O
designed	O
by	O
Microsoft	O
that	O
is	O
derived	O
from	O
Java	B-Language
1.1	O
)	O
,	O
A#	B-Language
(	O
from	O
Ada	B-Language
)	O
,	O
and	O
the	O
functional	B-Language
programming	I-Language
language	I-Language
F#	B-Operating_System
.	O
</s>
<s>
The	O
original	O
implementation	O
of	O
Eiffel	B-Application
for	I-Application
.NET	I-Application
was	O
called	O
Eiffel#	O
,	O
a	O
name	O
retired	O
since	O
the	O
full	O
Eiffel	B-Language
language	O
is	O
now	O
supported	O
.	O
</s>
<s>
The	O
suffix	O
has	O
also	O
been	O
used	O
for	O
libraries	B-Library
,	O
such	O
as	O
Gtk#	O
(	O
a	O
.NET	B-Application
wrapper	O
for	O
GTK	B-Application
and	O
other	O
GNOME	B-Application
libraries	B-Library
)	O
and	O
Cocoa#	B-Language
(	O
a	O
wrapper	O
for	O
Cocoa	B-Operating_System
)	O
.	O
</s>
<s>
The	O
core	O
syntax	O
of	O
the	O
C#	O
language	O
is	O
similar	O
to	O
that	O
of	O
other	O
C-style	O
languages	O
such	O
as	O
C	B-Language
,	O
C++	B-Language
and	O
Java	B-Language
,	O
particularly	O
:	O
</s>
<s>
Square	O
brackets	O
are	O
used	O
with	O
arrays	B-Data_Structure
,	O
both	O
to	O
declare	O
them	O
and	O
to	O
get	O
a	O
value	O
at	O
a	O
given	O
index	O
in	O
one	O
of	O
them	O
.	O
</s>
<s>
Some	O
notable	O
features	O
of	O
C#	O
that	O
distinguish	O
it	O
from	O
C	B-Language
,	O
C++	B-Language
,	O
and	O
Java	B-Language
where	O
noted	O
,	O
are	O
:	O
</s>
<s>
By	O
design	O
,	O
C#	O
is	O
the	O
programming	O
language	O
that	O
most	O
directly	O
reflects	O
the	O
underlying	O
Common	O
Language	O
Infrastructure(CLI )	O
.	O
</s>
<s>
However	O
,	O
the	O
language	O
specification	O
does	O
not	O
state	O
the	O
code	B-Application
generation	I-Application
requirements	O
of	O
the	O
compiler	B-Language
:	O
that	O
is	O
,	O
it	O
does	O
not	O
state	O
that	O
a	O
C#	O
compiler	B-Language
must	O
target	O
a	O
Common	O
Language	O
Runtime	O
,	O
or	O
generate	O
Common	O
Intermediate	O
Language	O
(	O
CIL	O
)	O
,	O
or	O
generate	O
any	O
other	O
specific	O
format	O
.	O
</s>
<s>
Theoretically	O
,	O
a	O
C#	O
compiler	B-Language
could	O
generate	O
machine	O
code	O
like	O
traditional	O
compilers	B-Language
of	O
C++	B-Language
or	O
Fortran	B-Application
.	O
</s>
<s>
C#	O
supports	O
strongly	O
,	O
implicitly	O
typed	O
variable	O
declarations	O
with	O
the	O
keyword	O
var	O
,	O
and	O
implicitly	O
typed	O
arrays	B-Data_Structure
with	O
the	O
keyword	O
new[]	O
followed	O
by	O
a	O
collection	O
initializer	O
.	O
</s>
<s>
C#	O
supports	O
a	O
strict	O
Boolean	O
data	O
type	O
,	O
bool	O
.	O
</s>
<s>
While	O
C++	B-Language
also	O
has	O
a	O
Boolean	O
type	O
,	O
it	O
can	O
be	O
freely	O
converted	O
to	O
and	O
from	O
integers	O
,	O
and	O
expressions	O
such	O
as	O
if	O
(	O
a	O
)	O
require	O
only	O
that	O
a	O
is	O
convertible	O
to	O
bool	O
,	O
allowing	O
a	O
to	O
be	O
an	O
int	O
,	O
or	O
a	O
pointer	O
.	O
</s>
<s>
C#	O
disallows	O
this	O
"	O
integer	O
meaning	O
true	O
or	O
false	O
"	O
approach	O
,	O
on	O
the	O
grounds	O
that	O
forcing	O
programmers	B-Application
to	O
use	O
expressions	O
that	O
return	O
exactly	O
bool	O
can	O
prevent	O
certain	O
types	O
of	O
programming	O
mistakes	O
such	O
as	O
if	O
(	O
a	O
=	O
b	O
)	O
(	O
use	O
of	O
assignment	O
=	O
instead	O
of	O
equality	O
==	O
)	O
.	O
</s>
<s>
C#	O
is	O
more	O
type	B-Language
safe	I-Language
than	O
C++	B-Language
.	O
</s>
<s>
This	O
is	O
enforced	O
at	O
compile-time	O
,	O
during	O
JIT	O
,	O
and	O
,	O
in	O
some	O
cases	O
,	O
at	O
runtime	O
.	O
</s>
<s>
No	O
implicit	O
conversions	O
occur	O
between	O
Booleans	O
and	O
integers	O
,	O
nor	O
between	O
enumeration	B-Language
members	O
and	O
integers	O
(	O
except	O
for	O
literal	O
0	O
,	O
which	O
can	O
be	O
implicitly	O
converted	O
to	O
any	O
enumerated	B-Language
type	I-Language
)	O
.	O
</s>
<s>
Any	O
user-defined	O
conversion	O
must	O
be	O
explicitly	O
marked	O
as	O
explicit	O
or	O
implicit	O
,	O
unlike	O
C++	B-Language
copy	B-Language
constructors	I-Language
and	O
conversion	O
operators	O
,	O
which	O
are	O
both	O
implicit	O
by	O
default	O
.	O
</s>
<s>
C#	O
has	O
explicit	O
support	O
for	O
covariance	O
and	O
contravariance	O
in	O
generic	B-Language
types	I-Language
,	O
unlike	O
C++	B-Language
which	O
has	O
some	O
degree	O
of	O
support	O
for	O
contravariance	O
simply	O
through	O
the	O
semantics	O
of	O
return	O
types	O
on	O
virtual	O
methods	O
.	O
</s>
<s>
Enumeration	B-Language
members	O
are	O
placed	O
in	O
their	O
own	O
scope	B-Language
.	O
</s>
<s>
The	O
C#	O
language	O
does	O
not	O
allow	O
for	O
global	O
variables	O
or	O
functions	O
.	O
</s>
<s>
Local	O
variables	O
cannot	O
shadow	B-Language
variables	O
of	O
the	O
enclosing	O
block	O
,	O
unlike	O
C	B-Language
and	O
C++	B-Language
.	O
</s>
<s>
Metaprogramming	B-Application
can	O
be	O
achieved	O
in	O
several	O
ways	O
:	O
</s>
<s>
Reflection	B-Language
is	O
supported	O
through	O
.NET	B-Application
APIs	O
,	O
which	O
enable	O
scenarios	O
such	O
as	O
type	O
metadata	O
inspection	O
and	O
dynamic	O
method	O
invocation	O
.	O
</s>
<s>
Expression	O
trees	O
represent	O
code	O
as	O
an	O
abstract	B-Data_Structure
syntax	I-Data_Structure
tree	I-Data_Structure
,	O
where	O
each	O
node	O
is	O
an	O
expression	O
that	O
can	O
be	O
inspected	O
or	O
executed	O
.	O
</s>
<s>
Attributes	B-General_Concept
are	O
metadata	O
that	O
can	O
be	O
attached	O
to	O
types	O
,	O
members	O
,	O
or	O
entire	O
assemblies	O
,	O
equivalent	O
to	O
annotations	B-Language
in	I-Language
Java	I-Language
.	O
</s>
<s>
Attributes	B-General_Concept
are	O
accessible	O
both	O
to	O
the	O
compiler	B-Language
and	O
to	O
code	O
through	O
reflection	B-Language
.	O
</s>
<s>
Many	O
of	O
these	O
attributes	B-General_Concept
duplicate	O
the	O
functionality	O
of	O
GCC	O
's	O
and	O
VisualC++'s	O
platform-dependent	O
preprocessor	O
directives	O
.	O
</s>
<s>
The	O
.NET	B-Application
Compiler	I-Application
Platform	I-Application
(	O
Roslyn	B-Application
)	O
provides	O
API	O
access	O
to	O
language	O
compilation	B-Language
services	O
,	O
allowing	O
for	O
the	O
compilation	B-Language
of	O
C#	O
code	O
from	O
within	O
.NET	B-Application
applications	O
.	O
</s>
<s>
It	O
exposes	O
APIs	O
for	O
syntactic	O
(	O
lexical	B-Application
)	O
analysis	O
of	O
code	O
,	O
semantic	O
analysis	O
,	O
dynamic	O
compilation	B-Language
to	O
CIL	O
,	O
and	O
code	O
emission	O
.	O
</s>
<s>
Source	O
generators	O
,	O
a	O
feature	O
of	O
the	O
Roslyn	B-Application
C#	O
compiler	B-Language
,	O
enable	O
compile	B-Language
time	O
metaprogramming	B-Application
.	O
</s>
<s>
During	O
the	O
compilation	B-Language
process	O
,	O
developers	B-Application
can	O
inspect	O
the	O
code	O
being	O
compiled	B-Language
with	O
the	O
compiler	B-Language
's	O
API	O
and	O
pass	O
additional	O
generated	O
C#	O
source	O
code	O
to	O
be	O
compiled	B-Language
.	O
</s>
<s>
A	O
method	O
in	O
C#	O
is	O
a	O
member	O
of	O
a	O
class	O
that	O
can	O
be	O
invoked	O
as	O
a	O
function	O
(	O
a	O
sequence	O
of	O
instructions	O
)	O
,	O
rather	O
than	O
the	O
mere	O
value-holding	O
capability	O
of	O
a	O
class	O
property	O
.	O
</s>
<s>
As	O
in	O
other	O
syntactically	O
similar	O
languages	O
,	O
such	O
as	O
C++	B-Language
and	O
ANSI	O
C	B-Language
,	O
the	O
signature	O
of	O
a	O
method	O
is	O
a	O
declaration	O
comprising	O
in	O
order	O
:	O
any	O
optional	O
accessibility	O
keywords	O
(	O
such	O
as	O
private	O
)	O
,	O
the	O
explicit	O
specification	O
of	O
its	O
return	O
type	O
(	O
such	O
as	O
int	O
,	O
or	O
the	O
keyword	O
void	O
if	O
no	O
value	O
is	O
returned	O
)	O
,	O
the	O
name	O
of	O
the	O
method	O
,	O
and	O
finally	O
,	O
a	O
parenthesized	O
sequence	O
of	O
comma-separated	O
parameter	O
specifications	O
,	O
each	O
consisting	O
of	O
a	O
parameter	O
's	O
type	O
,	O
its	O
formal	O
name	O
and	O
optionally	O
,	O
a	O
default	O
value	O
to	O
be	O
used	O
whenever	O
none	O
is	O
provided	O
.	O
</s>
<s>
Certain	O
specific	O
kinds	O
of	O
methods	O
,	O
such	O
as	O
those	O
that	O
simply	O
get	O
or	O
set	O
a	O
class	O
property	O
by	O
return	B-Language
value	I-Language
or	O
assignment	O
,	O
do	O
not	O
require	O
a	O
full	O
signature	O
,	O
but	O
in	O
the	O
general	O
case	O
,	O
the	O
definition	O
of	O
a	O
class	O
includes	O
the	O
full	O
signature	O
declaration	O
of	O
its	O
methods	O
.	O
</s>
<s>
Like	O
C++	B-Language
,	O
and	O
unlike	O
Java	B-Language
,	O
C#	O
programmers	B-Application
must	O
use	O
the	O
scope	B-Language
modifier	O
keyword	O
virtual	O
to	O
allow	O
methods	O
to	O
be	O
overridden	B-Language
by	O
subclasses	O
.	O
</s>
<s>
Extension	O
methods	O
in	O
C#	O
allow	O
programmers	B-Application
to	O
use	O
static	O
methods	O
as	O
if	O
they	O
were	O
methods	O
from	O
a	O
class	O
's	O
method	O
table	O
,	O
allowing	O
programmers	B-Application
to	O
add	O
methods	O
to	O
an	O
object	O
that	O
they	O
feel	O
should	O
exist	O
on	O
that	O
object	O
and	O
its	O
derivatives	O
.	O
</s>
<s>
The	O
type	O
dynamic	O
allows	O
for	O
run-time	O
method	O
binding	O
,	O
allowing	O
for	O
JavaScript-like	O
method	O
calls	O
and	O
run-time	O
object	B-Language
composition	I-Language
.	O
</s>
<s>
C#	O
has	O
support	O
for	O
strongly-typed	O
function	B-Language
pointers	I-Language
via	O
the	O
keyword	O
delegate	O
.	O
</s>
<s>
Like	O
the	O
Qt	O
framework	O
's	O
pseudo-C	O
++	O
signal	O
and	O
slot	O
,	O
C#	O
has	O
semantics	O
specifically	O
surrounding	O
publish-subscribe	O
style	O
events	O
,	O
though	O
C#	O
uses	O
delegates	O
to	O
do	O
so	O
.	O
</s>
<s>
C#	O
offers	O
Java-like	O
synchronized	O
method	O
calls	O
,	O
via	O
the	O
attribute	B-General_Concept
[	O
MethodImpl( 	O
MethodImplOptions.Synchronized	O
)	O
]	O
,	O
and	O
has	O
support	O
for	O
mutually-exclusive	B-Operating_System
locks	I-Operating_System
via	O
the	O
keyword	O
lock	O
.	O
</s>
<s>
C#	O
supports	O
classes	O
with	O
properties	B-Language
.	O
</s>
<s>
The	O
properties	B-Language
can	O
be	O
simple	O
accessor	O
functions	O
with	O
a	O
backing	O
field	O
,	O
or	O
implement	O
getter	O
and	O
setter	O
functions	O
.	O
</s>
<s>
Since	O
C#	B-Language
3.0	I-Language
the	O
syntactic	O
sugar	O
of	O
auto-implemented	O
properties	B-Language
is	O
available	O
,	O
where	O
the	O
accessor	O
(	O
getter	O
)	O
and	O
mutator	O
(	O
setter	O
)	O
encapsulate	O
operations	O
on	O
a	O
single	O
attribute	B-General_Concept
of	O
a	O
class	O
.	O
</s>
<s>
A	O
C#	O
namespace	O
provides	O
the	O
same	O
level	O
of	O
code	O
isolation	O
as	O
a	O
Java	B-Language
package	O
or	O
a	O
C++	B-Language
,	O
with	O
very	O
similar	O
rules	O
and	O
features	O
to	O
a	O
package	O
.	O
</s>
<s>
In	O
C#	O
,	O
memory	O
address	O
pointers	O
can	O
only	O
be	O
used	O
within	O
blocks	O
specifically	O
marked	O
as	O
unsafe	O
,	O
and	O
programs	O
with	O
unsafe	O
code	O
need	O
appropriate	O
permissions	O
to	O
run	O
.	O
</s>
<s>
Most	O
object	O
access	O
is	O
done	O
through	O
safe	O
object	O
references	O
,	O
which	O
always	O
either	O
point	O
to	O
a	O
"	O
live	O
"	O
object	O
or	O
have	O
the	O
well-defined	O
null	O
value	O
;	O
it	O
is	O
impossible	O
to	O
obtain	O
a	O
reference	O
to	O
a	O
"	O
dead	O
"	O
object	O
(	O
one	O
that	O
has	O
been	O
garbage	B-General_Concept
collected	I-General_Concept
)	O
,	O
or	O
to	O
a	O
random	O
block	O
of	O
memory	O
.	O
</s>
<s>
Managed	O
memory	O
cannot	O
be	O
explicitly	O
freed	O
;	O
instead	O
,	O
it	O
is	O
automatically	O
garbage	B-General_Concept
collected	I-General_Concept
.	O
</s>
<s>
Garbage	B-General_Concept
collection	I-General_Concept
addresses	O
the	O
problem	O
of	O
memory	B-Error_Name
leaks	I-Error_Name
by	O
freeing	O
the	O
programmer	B-Application
of	O
responsibility	O
for	O
releasing	O
memory	O
that	O
is	O
no	O
longer	O
needed	O
in	O
most	O
cases	O
.	O
</s>
<s>
Code	O
that	O
retains	O
references	O
to	O
objects	O
longer	O
than	O
is	O
required	O
can	O
still	O
experience	O
higher	O
memory	O
usage	O
than	O
necessary	O
,	O
however	O
once	O
the	O
final	O
reference	O
to	O
an	O
object	O
is	O
released	O
the	O
memory	O
is	O
available	O
for	O
garbage	B-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
A	O
range	O
of	O
standard	O
exceptions	O
are	O
available	O
to	O
programmers	B-Application
.	O
</s>
<s>
Methods	O
in	O
standard	O
libraries	B-Library
regularly	O
throw	O
system	O
exceptions	O
in	O
some	O
circumstances	O
and	O
the	O
range	O
of	O
exceptions	O
thrown	O
is	O
normally	O
documented	O
.	O
</s>
<s>
Checked	O
exceptions	O
are	O
not	O
present	O
in	O
C#	O
(	O
in	O
contrast	O
to	O
Java	B-Language
)	O
.	O
</s>
<s>
Unlike	O
C++	B-Language
,	O
C#	O
does	O
not	O
support	O
multiple	B-Application
inheritance	I-Application
,	O
although	O
a	O
class	O
can	O
implement	O
any	O
number	O
of	O
"	O
interfaces	B-Application
"	O
(	O
fully	O
abstract	O
classes	O
)	O
.	O
</s>
<s>
When	O
implementing	O
multiple	O
interfaces	B-Application
that	O
contain	O
a	O
method	O
with	O
the	O
same	O
name	O
and	O
taking	O
parameters	O
of	O
the	O
same	O
type	O
in	O
the	O
same	O
order	O
(	O
i.e.	O
</s>
<s>
the	O
same	O
signature	O
)	O
,	O
similar	O
to	O
Java	B-Language
,	O
C#	O
allows	O
both	O
a	O
single	O
method	O
to	O
cover	O
all	O
interfaces	B-Application
and	O
if	O
necessary	O
specific	O
methods	O
for	O
each	O
interface	O
.	O
</s>
<s>
However	O
,	O
unlike	O
Java	B-Language
,	O
C#	O
supports	O
operator	O
overloading	O
.	O
</s>
<s>
C#	O
has	O
the	O
ability	O
to	O
utilize	O
LINQ	B-Language
through	O
the	O
.NET	B-Application
Framework	I-Application
.	O
</s>
<s>
A	O
developer	B-Application
can	O
query	O
a	O
variety	O
of	O
data	O
sources	O
,	O
provided	O
IEnumerablexxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx1	O
interface	O
is	O
implemented	O
on	O
the	O
object	O
.	O
</s>
<s>
This	O
includes	O
XML	O
documents	O
,	O
an	O
ADO.NET	B-Device
dataset	O
,	O
and	O
SQL	O
databases	O
.	O
</s>
<s>
Using	O
LINQ	B-Language
in	O
C#	O
brings	O
advantages	O
like	O
Intellisense	B-Application
support	O
,	O
strong	O
filtering	O
capabilities	O
,	O
type	B-Language
safety	I-Language
with	O
compile	B-Language
error	O
checking	O
ability	O
,	O
and	O
consistency	O
for	O
querying	O
data	O
over	O
a	O
variety	O
of	O
sources	O
.	O
</s>
<s>
There	O
are	O
several	O
different	O
language	O
structures	O
that	O
can	O
be	O
utilized	O
with	O
C#	O
and	O
LINQ	B-Language
and	O
they	O
are	O
query	O
expressions	O
,	O
lambda	B-General_Concept
expressions	I-General_Concept
,	O
anonymous	B-Language
types	I-Language
,	O
implicitly	O
typed	O
variables	O
,	O
extension	O
methods	O
,	O
and	O
object	O
initializers	O
.	O
</s>
<s>
LINQ	B-Language
has	O
two	O
syntaxes	O
:	O
query	O
syntax	O
and	O
method	O
syntax	O
.	O
</s>
<s>
However	O
,	O
the	O
compiler	B-Language
always	O
converts	O
the	O
query	O
syntax	O
to	O
method	O
syntax	O
at	O
compile	B-Language
time	O
.	O
</s>
<s>
Though	O
primarily	O
an	O
imperative	B-Application
language	I-Application
,	O
C#	B-Language
2.0	I-Language
offered	O
limited	O
support	O
for	O
functional	B-Language
programming	I-Language
through	O
first-class	B-Application
functions	I-Application
and	O
closures	B-Language
in	O
the	O
form	O
of	O
anonymous	O
delegates	O
.	O
</s>
<s>
C#	B-Language
3.0	I-Language
expanded	O
support	O
for	O
functional	B-Language
programming	I-Language
with	O
the	O
introduction	O
of	O
a	O
lightweight	O
syntax	O
for	O
lambda	B-General_Concept
expressions	I-General_Concept
,	O
extension	O
methods	O
(	O
an	O
affordance	O
for	O
modules	O
)	O
,	O
and	O
a	O
list	B-Language
comprehension	I-Language
syntax	O
in	O
the	O
form	O
of	O
a	O
"	O
query	O
comprehension	O
"	O
language	O
.	O
</s>
<s>
C#	O
7.0	O
adds	O
features	O
typically	O
found	O
in	O
functional	B-Language
languages	I-Language
like	O
tuples	O
,	O
local	O
functions	O
and	O
pattern	B-Language
matching	I-Language
.	O
</s>
<s>
C#	O
9.0	O
introduces	O
record	O
feature	O
which	O
is	O
primarily	O
built	O
for	O
better	O
supporting	O
immutable	O
data	O
models	O
.	O
</s>
<s>
C#	O
has	O
a	O
unified	O
type	O
system	O
.	O
</s>
<s>
Some	O
other	O
limitations	O
on	O
value	O
types	O
are	O
that	O
they	O
cannot	O
derive	O
from	O
each	O
other	O
(	O
but	O
can	O
implement	O
interfaces	B-Application
)	O
and	O
cannot	O
have	O
an	O
explicit	O
default	O
(	O
parameterless	O
)	O
constructor	O
because	O
they	O
already	O
have	O
an	O
implicit	O
one	O
which	O
initializes	O
all	O
contained	O
data	O
to	O
the	O
type-dependent	O
default	O
value	O
(	O
0	O
,	O
null	O
,	O
or	O
alike	O
)	O
.	O
</s>
<s>
Other	O
examples	O
are	O
(	O
enumerations	B-Language
)	O
and	O
(	O
user	O
defined	O
structures	O
)	O
.	O
</s>
<s>
Examples	O
of	O
reference	O
types	O
are	O
(	O
the	O
ultimate	O
base	O
class	O
for	O
all	O
other	O
C#	O
classes	O
)	O
,	O
(	O
a	O
string	O
of	O
Unicode	O
characters	O
)	O
,	O
and	O
(	O
a	O
base	O
class	O
for	O
all	O
C#	O
arrays	B-Data_Structure
)	O
.	O
</s>
<s>
Both	O
type	O
categories	O
are	O
extensible	O
with	O
user-defined	B-Language
types	I-Language
.	O
</s>
<s>
Boxing	O
in	O
C#	O
is	O
implicit	O
.	O
</s>
<s>
Unboxing	O
in	O
C#	O
requires	O
an	O
explicit	O
type	O
cast	O
.	O
</s>
<s>
The	O
C#	O
specification	O
details	O
a	O
minimum	O
set	O
of	O
types	O
and	O
class	O
libraries	B-Library
that	O
the	O
compiler	B-Language
expects	O
to	O
have	O
available	O
.	O
</s>
<s>
In	O
practice	O
,	O
C#	O
is	O
most	O
often	O
used	O
with	O
some	O
implementation	O
of	O
the	O
Common	O
Language	O
Infrastructure	O
(	O
CLI	O
)	O
,	O
which	O
is	O
standardized	O
as	O
ECMA-335	O
Common	O
Language	O
Infrastructure	O
(	O
CLI	O
)	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
standard	O
CLI	O
specifications	O
,	O
there	O
are	O
many	O
commercial	O
and	O
community	O
class	O
libraries	B-Library
that	O
build	O
on	O
top	O
of	O
the	O
.NET	B-Application
framework	I-Application
libraries	B-Library
to	O
provide	O
additional	O
functionality	O
.	O
</s>
<s>
C#	O
can	O
make	O
calls	O
to	O
any	O
library	O
included	O
in	O
the	O
List	B-Application
of	I-Application
.NET	I-Application
libraries	I-Application
and	I-Application
frameworks	I-Application
.	O
</s>
<s>
The	O
following	O
is	O
a	O
very	O
simple	O
C#	O
program	O
,	O
a	O
version	O
of	O
the	O
classic	O
"	O
Hello	O
world	O
"	O
example	O
using	O
the	O
top-level	O
statements	O
feature	O
introduced	O
in	O
C#	O
9	O
:	O
</s>
<s>
For	O
code	O
written	O
as	O
C#	O
8	O
or	O
lower	O
,	O
the	O
entry	O
point	O
logic	O
of	O
a	O
program	O
must	O
be	O
written	O
in	O
a	O
Main	O
method	O
inside	O
a	O
type	O
:	O
</s>
<s>
This	O
line	O
is	O
a	O
comment	O
;	O
it	O
describes	O
and	O
documents	O
the	O
code	O
for	O
the	O
programmer(s )	O
.	O
</s>
<s>
The	O
.NET	B-Application
runtime	O
calls	O
the	O
method	O
.	O
</s>
<s>
Unlike	O
in	O
Java	B-Language
,	O
the	O
method	O
does	O
not	O
need	O
the	O
keyword	O
,	O
which	O
tells	O
the	O
compiler	B-Language
that	O
the	O
method	O
can	O
be	O
called	O
from	O
anywhere	O
by	O
any	O
class	O
.	O
</s>
<s>
Each	O
console	B-Device
application	I-Device
's	O
entry	O
point	O
must	O
be	O
declared	O
otherwise	O
the	O
program	O
would	O
require	O
an	O
instance	O
of	O
,	O
but	O
any	O
instance	O
would	O
require	O
a	O
program	O
.	O
</s>
<s>
To	O
avoid	O
that	O
irresolvable	O
circular	B-Language
dependency	I-Language
,	O
C#	O
compilers	B-Language
processing	O
console	B-Device
applications	I-Device
(	O
like	O
that	O
above	O
)	O
report	O
an	O
error	O
if	O
there	O
is	O
no	O
method	O
.	O
</s>
<s>
The	O
keyword	O
declares	O
that	O
has	O
no	O
return	B-Language
value	I-Language
.	O
</s>
<s>
It	O
provides	O
an	O
interface	O
to	O
the	O
standard	O
input	O
,	O
output	O
,	O
and	O
error	O
streams	O
for	O
console	B-Device
applications	I-Device
.	O
</s>
<s>
A	O
Windows	O
GUI	B-Application
example	O
:	O
</s>
<s>
In	O
August	O
2001	O
,	O
Microsoft	O
,	O
Hewlett-Packard	O
and	O
Intel	O
co-sponsored	O
the	O
submission	O
of	O
specifications	O
for	O
C#	O
as	O
well	O
as	O
the	O
Common	O
Language	O
Infrastructure	O
(	O
CLI	O
)	O
to	O
the	O
standards	O
organization	O
Ecma	O
International	O
.	O
</s>
<s>
In	O
December	O
2001	O
,	O
ECMA	O
released	O
ECMA-334	B-Application
C#	O
Language	O
Specification	O
.	O
</s>
<s>
C#	O
became	O
an	O
ISO/IEC	O
standard	O
in	O
2003	O
(	O
ISO/IEC	O
23270:2003	O
-	O
Information	O
technology	O
—	O
Programming	O
languages	O
—	O
C#	O
)	O
.	O
</s>
<s>
ECMA	O
had	O
previously	O
adopted	O
equivalent	O
specifications	O
as	O
the	O
2nd	O
edition	O
of	O
C#	O
,	O
in	O
December	O
2002	O
.	O
</s>
<s>
In	O
June	O
2005	O
,	O
ECMA	O
approved	O
edition	O
3	O
of	O
the	O
C#	O
specification	O
,	O
and	O
updated	O
ECMA-334	B-Application
.	O
</s>
<s>
Additions	O
included	O
partial	O
classes	O
,	O
anonymous	B-General_Concept
methods	I-General_Concept
,	O
nullable	O
types	O
,	O
and	O
generics	B-Language
(	O
somewhat	O
similar	O
to	O
C++	B-Application
templates	I-Application
)	O
.	O
</s>
<s>
The	O
C#	O
language	O
definition	O
and	O
the	O
CLI	O
are	O
standardized	O
under	O
ISO/IEC	O
and	O
Ecma	O
standards	O
that	O
provide	O
reasonable	O
and	O
non-discriminatory	O
licensing	O
protection	O
from	O
patent	O
claims	O
.	O
</s>
<s>
Microsoft	O
has	O
also	O
agreed	O
not	O
to	O
enforce	O
patents	O
relating	O
to	O
Novell	O
products	O
against	O
Novell	O
's	O
paying	O
customers	O
with	O
the	O
exception	O
of	O
a	O
list	O
of	O
products	O
that	O
do	O
not	O
explicitly	O
mention	O
C#	O
,	O
.NET	B-Application
or	O
Novell	O
's	O
implementation	O
of	O
.NET	B-Application
(	O
The	B-Application
Mono	I-Application
Project	I-Application
)	O
.	O
</s>
<s>
However	O
,	O
Novell	O
maintained	O
that	O
Mono	B-Application
does	O
not	O
infringe	O
any	O
Microsoft	O
patents	O
.	O
</s>
<s>
Microsoft	O
also	O
made	O
a	O
specific	O
agreement	O
not	O
to	O
enforce	O
patent	O
rights	O
related	O
to	O
the	O
Moonlight	B-Language
browser	I-Language
plugin	I-Language
,	O
which	O
depends	O
on	O
Mono	B-Application
,	O
provided	O
it	O
is	O
obtained	O
through	O
Novell	O
.	O
</s>
<s>
A	O
decade	O
later	O
,	O
Microsoft	O
began	O
developing	O
free	O
,	O
open-source	B-Application
,	O
and	O
cross-platform	B-Operating_System
tooling	O
for	O
C#	O
,	O
namely	O
Visual	B-Language
Studio	I-Language
Code	I-Language
,	O
.NET	B-Application
Core	I-Application
,	O
and	O
Roslyn	B-Application
.	O
</s>
<s>
Mono	B-Application
joined	O
Microsoft	O
as	O
a	O
project	O
of	O
Xamarin	B-Application
,	O
a	O
Microsoft	O
subsidiary	O
.	O
</s>
<s>
Microsoft	O
is	O
leading	O
the	O
development	O
of	O
the	O
open-source	B-Application
reference	O
C#	O
compilers	B-Language
and	O
set	O
of	O
tools	O
.	O
</s>
<s>
The	O
first	O
compiler	B-Language
,	O
Roslyn	B-Application
,	O
compiles	B-Language
into	O
intermediate	O
language	O
(	O
IL	O
)	O
,	O
and	O
the	O
second	O
one	O
,	O
RyuJIT	O
,	O
is	O
a	O
JIT	O
(	O
just-in-time	O
)	O
compiler	B-Language
,	O
which	O
is	O
dynamic	O
and	O
does	O
on-the-fly	O
optimization	O
and	O
compiles	B-Language
the	O
IL	O
into	O
native	O
code	O
for	O
the	O
front-end	O
of	O
the	O
CPU	O
.	O
</s>
<s>
RyuJIT	O
is	O
open	O
source	O
and	O
written	O
in	O
C++	B-Language
.	O
</s>
<s>
Roslyn	B-Application
is	O
entirely	O
written	O
in	O
managed	O
code	O
(	O
C#	O
)	O
,	O
has	O
been	O
opened	O
up	O
and	O
functionality	O
surfaced	O
as	O
APIs	O
.	O
</s>
<s>
It	O
is	O
thus	O
enabling	O
developers	B-Application
to	O
create	O
refactoring	O
and	O
diagnostics	O
tools	O
.	O
</s>
<s>
Two	O
branches	O
of	O
official	O
implementation	O
are	O
.NET	B-Application
Framework	I-Application
(	O
closed-source	B-Application
,	O
Windows-only	O
)	O
and	O
.NET	B-Application
Core	I-Application
(	O
open-source	B-Application
,	O
cross-platform	B-Operating_System
)	O
;	O
they	O
eventually	O
converged	O
into	O
one	O
open-source	B-Application
implementation	O
:	O
.NET	O
5.0	O
.	O
</s>
<s>
At	O
.NET	B-Application
Framework	I-Application
4.6	O
,	O
a	O
new	O
JIT	O
compiler	B-Language
replaced	O
the	O
former	O
.	O
</s>
<s>
Other	O
C#	O
compilers	B-Language
(	O
some	O
of	O
which	O
include	O
an	O
implementation	O
of	O
the	O
Common	O
Language	O
Infrastructure	O
and	O
.NET	B-Application
class	O
libraries	B-Library
)	O
:	O
</s>
<s>
Mono	B-Application
,	O
a	O
Microsoft-sponsored	O
project	O
provides	O
an	O
open-source	B-Application
C#	O
compiler	B-Language
,	O
a	O
complete	O
open-source	B-Application
implementation	O
of	O
the	O
CLI	O
(	O
including	O
the	O
required	O
framework	O
libraries	B-Library
as	O
they	O
appear	O
in	O
the	O
ECMA	O
specification	O
,	O
)	O
and	O
a	O
nearly	O
complete	O
implementation	O
of	O
the	O
NET	O
class	O
libraries	B-Library
up	O
to	O
.NET	B-Application
Framework	I-Application
3.5	O
.	O
</s>
<s>
The	O
Elements	O
tool	O
chain	O
from	O
RemObjects	O
includes	O
RemObjects	O
C#	O
,	O
which	O
compiles	B-Language
C#	O
code	O
to	O
.NET	B-Application
'	O
s	O
Common	O
Intermediate	O
Language	O
,	O
Java	B-Language
bytecode	I-Language
,	O
Cocoa	B-Operating_System
,	O
Android	B-Application
bytecode	I-Application
,	O
WebAssembly	B-Language
,	O
and	O
native	O
machine	O
code	O
for	O
Windows	O
,	O
macOS	O
,	O
and	O
Linux	O
.	O
</s>
<s>
The	O
DotGNU	B-Application
project	O
(	O
now	O
discontinued	O
)	O
also	O
provided	O
an	O
open-source	B-Application
C#	O
compiler	B-Language
,	O
a	O
nearly	O
complete	O
implementation	O
of	O
the	O
Common	O
Language	O
Infrastructure	O
including	O
the	O
required	O
framework	O
libraries	B-Library
as	O
they	O
appear	O
in	O
the	O
ECMA	O
specification	O
,	O
and	O
subset	O
of	O
some	O
of	O
the	O
remaining	O
Microsoft	O
proprietary	B-Application
.NET	B-Application
class	O
libraries	B-Library
up	O
to	O
.NET	B-Application
2.0	O
(	O
those	O
not	O
documented	O
or	O
included	O
in	O
the	O
ECMA	O
specification	O
,	O
but	O
included	O
in	O
Microsoft	O
's	O
standard	O
.NET	B-Application
Framework	I-Application
distribution	O
)	O
.	O
</s>
<s>
The	O
Unity	B-Application
game	I-Application
engine	I-Application
uses	O
C#	O
as	O
its	O
primary	O
scripting	O
language	O
.	O
</s>
<s>
The	O
Godot	B-Application
game	I-Application
engine	I-Application
has	O
implemented	O
an	O
optional	O
C#	O
module	O
thanks	O
to	O
a	O
donation	O
of	O
$	O
24,000	O
from	O
Microsoft	O
.	O
</s>
