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Direct casting vs 'as' operator?
Casting vs. using the as keyword in the CLR
In C#, whats the difference
var obj = (Array)Something
vs
var obj = Something as Array
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3This is a dupe of many [questions](http://stackoverflow.com/questions/496096/casting-vs-using-the-as-keyword-in-the-clr) here. Is no one ever reading the documentation these days? – Dirk Vollmar Oct 05 '10 at 08:29
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1first hit when searching this site for `[c#] typecast` showed this: http://stackoverflow.com/questions/3724051/what-is-difference-between-normal-typecasting-and-using-as-keyword-closed which in turn is closed as a dup of other questions. Voting for closing – Isak Savo Oct 05 '10 at 08:33
3 Answers
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first will throw a CastException if invalid. The second will only result in obj = null instead.
danijels
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1No the second will result in an object of the correct type or null. You are thinking of the `is` operator, Arcturus. – Matt Ellen Oct 05 '10 at 08:32
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no, the second will result in obj variable not being assigned any value because the cast failed. Thus, obj will be null – danijels Oct 05 '10 at 08:32
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1I know Matt, but `obj = null` so `obj == null` is `true`. One = sign too many :) – Arcturus Oct 05 '10 at 08:32
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I think danijels means that the second code example in the OP will mean that obj will equal null, or obj == null :) – Matt Ellen Oct 05 '10 at 08:41
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exactly, Matt. I don't see the confusion here really. Looking at the smiley at the end of first comment, I can only assume the guy was trying to be cute... – danijels Oct 05 '10 at 08:43
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var obj = (Array)Something
will throw an InvalidCastExcpetion if Something not derived from System.Array or does not have a conversion operator for System.Array. This can be used with value types and reference types.
var obj = Something as Array
will return null (obj will be null) if Something not derived from System.Array or does not have a conversion operator for System.Array. This can be used only with reference types. You'd need to box you value type first.
bitbonk
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As well as Danijels answers
The first can be used with any type.
The as operator can only be used on reference types.
Matt Ellen
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