Object creation in C# question

Question

I'm going over some c# tutorial that states the following:

"After it finds the attribute class, the compiler will check whether the attribute is allowed on a class. Then it will check for a constructor that matches the parameters specified in the attribute use. If it finds one, it creates an instance of the object by calling the constructor with the specified values"

The name of this paragraph is "compilation process", and it refers to the way the compiler handles attributes. I'm sorry for the ignorance, but shouldn't instances be created at run time?

Thanks.

Searching for that quote returns exactly 1 result: this question. Where did you get it from? — dtb
– dtb, Commented Nov 21, 2010 at 16:07
It sounds like compiler here is being used as a synonym for "code the compiler generates". — Hogan
– Hogan, Commented Nov 21, 2010 at 17:38

Rowland Shaw · Accepted Answer · 2010-11-21 16:12:18Z

3

Attributes define metadata for classes -- every instance of the class (i.e. object) will share the same attribute values. This metadata is stored alongside the type definition, which is calculated once at compile time from the source files.

answered Nov 21, 2010 at 16:12

Rowland Shaw

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Vilx- · Accepted Answer · 2010-11-21 16:19:26Z

2

Since there are attributes that also affect the compiler, I wouldn't be surprised if the compiler did instantiate them when compiling. So what?

answered Nov 21, 2010 at 16:19

Vilx-

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6 Comments

user429400 Over a year ago

I didn't know that the compiler instantiates objects.

CodesInChaos Over a year ago

Sounds rather unlikely. I doubt that the compiler instantiates attributes(i.e. it calls the constructor of a user defined attribute).

miguel Over a year ago

how would a compiler instantiate an object??

Vilx- Over a year ago

@miguel - compile the class, then fire up .NET and instantiate it? O_o

miguel Over a year ago

that is not the compiler instantiating an object. that is the runtime.

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AmineDZ · Accepted Answer · 2010-11-21 16:09:23Z

1

There is a "compilation" process that generates an intermediary code which is interpreted using .NET framework.

That's why they are talking about compilation process.

answered Nov 21, 2010 at 16:09

AmineDZ

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CodesInChaos · Accepted Answer · 2010-11-21 17:24:27Z

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The compiler only creates metadata which describes the attribute construction and assignments to its properties. The attribute itself is only instantiated at the time you use reflection to list attributes. I think each call to reflection creates a new instance of that attribute.

And I think there is a way(related to reflection only contexts) to check the attribute directly from the meta without instantiating it at all.

answered Nov 21, 2010 at 17:24

CodesInChaos

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