c# Casting v As operator

Nagy Vilmos

I prefer as because it is safer:

expression as type

is equivalent to:

expression is type ? (type)expression : (type)null

When you use casting you can get StoopidTypeException.

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NormDroid

a. Throw back from C++ programming.

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NormDroid

Good point.

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Ravi Bhavnani

It depends. (A) will throw if the cast fails while (B) will evaluate to null if the cast fails. I use both depending on how I intend to handle the casting failure. /ravi

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W Balboos GHB

Sorry - wrong. The answer's a, because it's better.

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Nagy Vilmos

Norm .net wrote:

Good point.

Holy cr_p! I'm going to the pub, we'll see what comes out after lunch! :laugh:

Panic, Chaos, Destruction. My work here is done. Drink. Get drunk. Fall over - P O'H OK, I will win to day or my name isn't Ethel Crudacre! - DD Ethel Crudacre I cannot live by bread alone. Bacon and ketchup are needed as well. - Trollslayer Have a bit more patience with newbies. Of course some of them act dumb - they're often *students*, for heaven's sake - Terry Pratchett

hairy_hats

Which is exactly why this is more of a programming question than a "lifestyle choice" question.

Pete OHanlon

It depends on the situation. Normally, I prefer to cast with the as operator because I don't have to catch the exception, and it just feels more natural for me to not have code like this:

MyClass c = null;
try
{
c = (MyClass)variable;
}
catch(InvalidCastException)
{
c = new MyClass();
}

Of course, there are times where you can't use as, so in those cases you use the () casting form.

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NormDroid

True, but you should know beforehand if the casting is correct.

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realJSOP

Correct answer.

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hairy_hats

No, because the two are not equivalent (see other posts below).

Peter Mulholland

I did not know this. I'm currently working on stuff with a common base interface with multipe derived interfaces and I've been playing about with GetType and typeof to try to get the correct derived interface from a base interface. So reading lounge posts may have been productive today. :-D

Pete

hairy_hats

If a noob had asked that question in the Lounge they'd have been toast.

Ravi Bhavnani

Norm .net wrote:

True, but you should know beforehand if the casting is correct.

"Should" is a dangerous word. :) A plugin discovery mechanism (that makes extensive use of reflection) I recently built assumes nothing regarding the type of object that was loaded. /ravi

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Aamir Butt

B. Because apart from what others have mentioned in favor of b, it will automagically do a QueryInterface as well in case of a COM interface call.

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NormDroid

It's a debate, not a question.

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Nagy Vilmos

There seems to be alot of white space in your sig.

Panic, Chaos, Destruction. My work here is done. Drink. Get drunk. Fall over - P O'H OK, I will win to day or my name isn't Ethel Crudacre! - DD Ethel Crudacre I cannot live by bread alone. Bacon and ketchup are needed as well. - Trollslayer Have a bit more patience with newbies. Of course some of them act dumb - they're often *students*, for heaven's sake - Terry Pratchett

NormDroid

Good point, I suppose not many noobies would know about QueryInterface, ah those were the days. :)

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Aamir Butt

Yeah... I always ended up using CComPtr to avoid reference-leak issues. MS should have banned direct use of QueryInterface and CoCreateInstance anyway. RAII should have been the way from onset.

A year spent in artificial intelligence is enough to make one believe in God

Richard A Dalton

If an illegal cast is an exceptional (woah, that should never happen) situation, then (a) If there's a possibility that through normal use the cast might be invalid (e.g. Plug-in tpye code), then (b), followed by an If to check for Null. -Richard

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