Casting / AS

[John Sutor]

Does anyone know the difference between Casting and using "AS" ?

[Niki Estner]

C# programmers reference - as operator:
....
Remarks:
The as operator is like a cast except that it yields null on conversion
failure instead of raising an exception. More formally, an expression of the
form:

expression as typeis equivalent to:

expression is type ? (type)expression : (type)nullexcept that expression is
evaluated only once.

Note that the as operator only performs reference conversions and boxing
conversions. The as operator cannot perform other conversions, such as
user-defined conversions, which should instead be performed using cast
expressions.
"John Sutor" <jo********@cinfin.com> wrote in
news:e8**************@TK2MSFTNGP09.phx.gbl...

Does anyone know the difference between Casting and using "AS" ?

[Jon Skeet [C# MVP]]

John Sutor <jo********@cinfin.com> wrote:

Does anyone know the difference between Casting and using "AS" ?

See http://www.yoda.arachsys.com/csharp/faq/#cast.as

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[John Wood]

A good example of where you might use AS is when you're testing to see if an
instance implements a specific interface, and to get hold of that interface
instance at the same time.
eg.

IWalks walker = animal as IWalks;
if (walks!=null)
{
... do something with 'walker'
}

Which is a little bit more efficient (when the instance does support the
interface) than the equivalent code:

if (animal is IWalks)
{
IWalks walker = (IWalks)animal;
... do something with 'walker'
}

--
John Wood
EMail: first name, dot, second name at priorganize.com
"John Sutor" <jo********@cinfin.com> wrote in message
news:e8**************@TK2MSFTNGP09.phx.gbl...

Does anyone know the difference between Casting and using "AS" ?

[John Wood]

I should point out that the line:

if (walks!=null) ....should have been:
if (walker!=null)

(before Mr Skeet points it out for me >:)

--
John Wood
EMail: first name, dot, second name at priorganize.com
"John Wood" <sp**@isannoying.com> wrote in message
news:eB**************@TK2MSFTNGP09.phx.gbl... A good example of where you might use AS is when you're testing to see if an instance implements a specific interface, and to get hold of that interface instance at the same time.
eg.

IWalks walker = animal as IWalks;
if (walks!=null)
{
... do something with 'walker'
}

Which is a little bit more efficient (when the instance does support the
interface) than the equivalent code:

if (animal is IWalks)
{
IWalks walker = (IWalks)animal;
... do something with 'walker'
}

--
John Wood
EMail: first name, dot, second name at priorganize.com
"John Sutor" <jo********@cinfin.com> wrote in message
news:e8**************@TK2MSFTNGP09.phx.gbl...

Does anyone know the difference between Casting and using "AS" ?