<s>
Visual	B-Application
Studio	I-Application
Tools	I-Application
for	I-Application
Office	I-Application
(	O
VSTO	O
)	O
is	O
a	O
set	O
of	O
development	O
tools	O
available	O
in	O
the	O
form	O
of	O
a	O
Visual	B-Application
Studio	I-Application
add-in	O
(	O
project	O
templates	O
)	O
and	O
a	O
runtime	B-Library
that	O
allows	O
Microsoft	B-General_Concept
Office	I-General_Concept
2003	I-General_Concept
and	O
later	O
versions	O
of	O
Office	O
applications	O
to	O
host	O
the	O
.NET	B-Application
Framework	I-Application
Common	O
Language	O
Runtime	B-Library
(	O
CLR	O
)	O
to	O
expose	O
their	O
functionality	O
via	O
.NET	B-Application
.	O
</s>
<s>
This	O
allows	O
extensions	O
to	O
the	O
Office	O
applications	O
to	O
be	O
written	O
in	O
CLI	B-Language
compliant	I-Language
languages	I-Language
as	O
well	O
as	O
to	O
use	O
functionality	O
and	O
user	O
interface	O
constructs	O
from	O
Office	O
applications	O
in	O
.NET	B-Application
applications	O
.	O
</s>
<s>
Extensions	O
to	O
Office	O
prior	O
to	O
Office	B-General_Concept
2003	I-General_Concept
only	O
allowed	O
the	O
creation	O
of	O
COM	B-Application
add-ins	O
using	O
Visual	B-Language
Basic	I-Language
or	O
Visual	B-Application
C++	I-Application
and	O
a	O
"	O
Developer	O
"	O
edition	O
was	O
also	O
offered	O
that	O
enabled	O
VBA	B-Language
developers	O
to	O
create	O
COM	B-Application
Add-ins	O
.	O
</s>
<s>
The	O
developer	O
editions	O
of	O
Office	O
have	O
been	O
discontinued	O
after	O
Office	O
XP	O
and	O
VSTO	O
is	O
available	O
for	O
Office	B-General_Concept
2003	I-General_Concept
and	O
later	O
versions	O
only	O
.	O
</s>
<s>
The	O
VSTO	O
runtime	B-Library
,	O
although	O
part	O
of	O
VSTO	O
development	O
tools	O
,	O
is	O
also	O
downloadable	O
separately	O
if	O
required	O
.	O
</s>
<s>
COM	B-Application
addin	O
development	O
is	O
still	O
possible	O
for	O
Office	O
2000	O
and	O
all	O
later	O
versions	O
using	O
the	O
Shared	O
Add-in	O
template	O
in	O
any	O
version	O
of	O
Microsoft	B-Application
Visual	I-Application
Studio	I-Application
.	O
</s>
<s>
The	O
VSTO	O
add-ins	O
(	O
project	O
types	O
and	O
controls	O
)	O
are	O
also	O
developed	O
using	O
Visual	B-Application
Studio	I-Application
.	O
</s>
<s>
For	O
Visual	B-Application
Studio	I-Application
.NET	B-Application
2003	B-General_Concept
and	O
Visual	B-Application
Studio	I-Application
2005	O
,	O
it	O
was	O
available	O
only	O
as	O
a	O
standalone	O
edition	O
with	O
support	O
for	O
.NET	B-Language
languages	I-Language
limited	O
to	O
Visual	O
Basic.NET	O
and	O
C#	O
.	O
</s>
<s>
It	O
was	O
also	O
included	O
as	O
a	O
part	O
of	O
the	O
Visual	B-Application
Studio	I-Application
Team	I-Application
System	I-Application
2005	O
.	O
</s>
<s>
Later	O
on	O
,	O
the	O
Visual	B-Application
Studio	I-Application
Tools	I-Application
for	I-Application
Office	I-Application
2005	O
Second	O
Edition	O
(	O
VSTO	O
2005	O
SE	O
)	O
was	O
released	O
as	O
a	O
free	O
add-in	O
to	O
Visual	B-Application
Studio	I-Application
Professional	O
and	O
above	O
that	O
includes	O
Office	O
2007	O
and	O
2003	B-General_Concept
support	O
.	O
</s>
<s>
However	O
,	O
for	O
Visual	B-Application
Studio	I-Application
Professional	O
Edition	O
,	O
it	O
installs	O
only	O
the	O
application-level	O
add-ins	O
;	O
it	O
does	O
not	O
add	O
the	O
document-level	O
customizations	O
or	O
other	O
functionality	O
(	O
actions	O
pane	O
,	O
host	O
controls	O
,	O
visual	O
document	O
designer	O
,	O
etc	O
.	O
)	O
</s>
<s>
The	O
current	O
version	O
is	O
Visual	B-Application
Studio	I-Application
Tools	I-Application
for	I-Application
Office	I-Application
2012	O
(	O
VSTO	O
4.5	O
)	O
which	O
is	O
compatible	O
with	O
Office	O
2016	O
,	O
Office	O
2013	O
,	O
Office	O
2010	O
,	O
and	O
Office	O
2007	O
.	O
</s>
<s>
Like	O
VBA	B-Language
,	O
code	O
written	O
for	O
VSTO	O
is	O
executed	O
by	O
a	O
separate	O
virtual	B-Architecture
machine	I-Architecture
(	O
the	O
CLR	O
)	O
which	O
is	O
hosted	O
inside	O
the	O
Microsoft	B-Application
Office	I-Application
applications	O
.	O
</s>
<s>
However	O
,	O
unlike	O
VBA	B-Language
,	O
where	O
the	O
code	O
is	O
stored	O
in	O
the	O
document	O
file	O
itself	O
,	O
programs	O
written	O
with	O
VSTO	O
are	O
stored	O
in	O
separate	O
CLI	O
assemblies	O
which	O
are	O
associated	O
with	O
the	O
documents	O
by	O
means	O
of	O
custom	O
properties	O
.	O
</s>
<s>
If	O
the	O
properties	O
are	O
present	O
,	O
Microsoft	B-Application
Office	I-Application
hosts	O
the	O
CLR	O
and	O
loads	O
the	O
assembly	O
specified	O
in	O
the	O
property	O
into	O
a	O
separate	O
appdomain	B-Architecture
named	O
after	O
the	O
document	O
's	O
name	O
.	O
</s>
<s>
VSTO	O
applications	O
are	O
subject	O
to	O
the	O
.NET	B-Application
Framework	I-Application
Code	O
Access	O
Security	O
constraints	O
,	O
in	O
addition	O
to	O
the	O
digital	O
signature	O
based	O
permission	O
model	O
that	O
governs	O
VBA	B-Language
macros	I-Language
.	O
</s>
<s>
VSTO	O
development	O
is	O
normally	O
performed	O
using	O
Visual	B-Application
Studio	I-Application
as	O
used	O
by	O
professional	O
programmers	O
.	O
</s>
<s>
VBA	B-Language
is	O
normally	O
developed	O
from	O
within	O
the	O
Office	O
application	O
and	O
requires	O
no	O
special	O
tools	O
.	O
</s>
<s>
VBA	B-Language
also	O
has	O
a	O
macro	O
recorder	O
that	O
can	O
generate	O
VBA	B-Language
code	O
from	O
user	O
actions	O
which	O
is	O
useful	O
for	O
non-professional	O
programmers	O
.	O
</s>
<s>
VSTO	O
is	O
Microsoft	O
.NET	B-Application
technology	O
and	O
add-ins	O
using	O
JavaScript	O
API	O
technology	O
use	O
JavaScript	O
,	O
HTML	O
and	O
CSS	O
.	O
</s>
<s>
The	O
latest	O
version	O
of	O
VSTO	O
,	O
as	O
of	O
2018	O
,	O
is	O
"	O
Office	O
Tools	O
for	O
Visual	B-Application
Studio	I-Application
"	O
and	O
is	O
available	O
with	O
all	O
versions	O
of	O
Microsoft	B-Application
Visual	I-Application
Studio	I-Application
2017	O
.	O
</s>
<s>
VSTO	O
2003	B-General_Concept
,	O
2005	O
,	O
3.0	O
and	O
2010	O
runtimes	O
install	O
in	O
side-by-side	O
(	O
SxS	O
)	O
mode	O
.	O
</s>
<s>
VSTO	O
2005	O
SE	O
runtime	B-Library
replaces	O
the	O
earlier	O
VSTO	O
2005	O
runtime	B-Library
.	O
</s>
<s>
VSTO	O
2010	O
runtime	B-Library
installs	O
side-by-side	O
with	O
VSTO	O
3.0	O
,	O
however	O
,	O
Office	O
2007	O
applications	O
can	O
also	O
use	O
the	O
VSTO	O
2010	O
runtime	B-Library
.	O
</s>
<s>
All	O
older	O
VSTO	O
solutions	O
will	O
continue	O
to	O
run	O
in	O
newer	O
versions	O
of	O
Office	O
as	O
long	O
as	O
the	O
runtime	B-Library
against	O
which	O
they	O
were	O
developed	O
is	O
installed	O
.	O
</s>
<s>
Office	O
2010	O
applications	O
will	O
always	O
use	O
VSTO	O
2010	O
Runtime	B-Library
.	O
</s>
<s>
Code	O
developed	O
with	O
various	O
editions	O
of	O
VSTO	O
will	O
only	O
work	O
with	O
certain	O
releases	O
and	O
editions	O
of	O
Microsoft	B-General_Concept
Office	I-General_Concept
2003	I-General_Concept
and	O
related	O
products	O
.	O
</s>
<s>
Specifically	O
,	O
VSTO	O
solutions	O
developed	O
in	O
editions	O
prior	O
to	O
VSTO	O
2005	O
SE	O
will	O
not	O
work	O
with	O
any	O
edition	O
of	O
Office	B-General_Concept
2003	I-General_Concept
other	O
than	O
Professional	O
.	O
</s>
<s>
VSTO	O
solutions	O
developed	O
with	O
VSTO	O
2005	O
SE	O
will	O
work	O
with	O
Office	B-General_Concept
2003	I-General_Concept
Standard	O
(	O
only	O
application-level	O
add-ins	O
)	O
and	O
Professional	O
.	O
</s>
