Re: [ADVANCED-DOTNET] When does the attribute contructor gets executed??

Girish Jain Tue, 18 Jan 2005 23:22:37 -0800

Hi All,

My basic understanding about attributes was wrong and you guys helped me
correct it.

Now I am doing it this way..
When the class, which is using the global data associated with a Type,
doesn't find any data for the given type, enumerates through all the public
properties/fields of the Type.

Thanks a lot!!

Regards,
Girish Jain

From: Eric Gunnerson <[EMAIL PROTECTED]>
Reply-To: "Unmoderated discussion of advanced .NET topics."
<ADVANCED-DOTNET@DISCUSS.DEVELOP.COM>
To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM
Subject: Re: [ADVANCED-DOTNET] When does the attribute contructor gets
executed??
Date: Tue, 18 Jan 2005 12:03:32 -0800

"Serialization" isn't really the right term.

Attributes use a special format to save their data that isn't related to
the .NET serialization infrastructure (s).

We used "pickling" as the term, but I'm not sure where that came from.

Eric

-----Original Message-----
From: Unmoderated discussion of advanced .NET topics.
[mailto:[EMAIL PROTECTED] On Behalf Of Fred Palmer
Sent: Tuesday, January 18, 2005 6:49 AM
To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM
Subject: Re: [ADVANCED-DOTNET] When does the attribute contructor gets
executed??

Thanks for stepping in Wallace.  So the constructor does get called, and
my last comment was inaccurate.  It's not the instance that's
serialized.

Thanks,
Fred

> Girish,
>
> As you discovered, the attribute declaration does not cause the
> constructor
> to execute. You would need to call GetCustomAttribute on each member
in
> order for the constructor of the corresponding attribute to be called.
>
> According to Essential .NET,
>
>     "Custom attributes are stored as passive BLOBs in the
>     CLR metadata. These BLOBs represent serialized
>     constructor calls to the attribute type...  Calling
>     GetCustomAttributes causes the serialized attribute
>     constructors to execute as the attribute objects are
>     instantiated from the metadata prior to your code seeing
>     them."
>
> Stepping through the attached code illustrates this.
>
> Wally
>
> using System;
> using System.Reflection;
>
> class MyAttribute : Attribute
> {
>     static int counter = 0;
>     public MyAttribute()
>     {
>         Console.WriteLine("In constructor of attribute #{0}.",
>             ++MyAttribute.counter);
>     }
> }
>
> [MyAttribute]
> class MyClass : Object
> {
>     [MyAttribute]
>     public int i;
>
>     [MyAttribute]
>     public int j;
> }
>
> class MyApp
> {
>     static void Main()
>     {
>         Type myType = typeof(MyClass);
>         MyClass myClass = new MyClass();
>         MemberInfo[] memberInfos = myType.GetMembers();
>         foreach(MemberInfo mi in memberInfos)
>         {
>             // Custom attribute constructor called
>             // in the following method
>             mi.GetCustomAttributes(false);
>         }
>     }
> }
>
> -----Original Message-----
> From: Unmoderated discussion of advanced .NET topics.
> [mailto:[EMAIL PROTECTED] On Behalf Of Girish Jain
> Sent: Tuesday, January 18, 2005 7:19 AM
> To: ADVANCED-DOTNET@DISCUSS.DEVELOP.COM
> Subject: [ADVANCED-DOTNET] When does the attribute contructor gets
> executed??
>
> Hi All,
>
> I have written a custom attribute and applied it to the public
> fields/properties of a class. This attribute actually maintains
certain
> data
> per **Type**.
>
> In the constructor of this attribute class I am adding data to a
static
> HashTable object, declared in the attribute class (Certainly, after
> checking
> that it does not already exist for the given Type)
>
> For example :
>
> public class A
> {
>     [MyCustom("some data...")]
>     public int i;
>
>    [MyCustom("some data...")]
>    public string Name
>    {
>         get { return this._ColName; }
>        set { this._ColName = value; }
>    }
> }
>
> I expect the attribute constructor to have already executed by the
time I
> create the first instance of the class A. But it is not happening.
>
>
> Can anybody tell me when does the constructor for the attribute gets
> executed?
>
> Thanks in advance
>
> Regards,
> Girish Jain
>
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Re: [ADVANCED-DOTNET] When does the attribute contructor gets executed??

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