Hi Vikas,
Please go thru this. It may Helps you to some extent.
1)Attributes
-->Attributes are a mechanism for adding metadata to the program
itself.
-->Attributes allow developers to add descriptions to classes,
properties, and methods at design time that can then be examined at
runtime
-->Attributes are inserted into the metadata and are visible through
ILDasm metadata-reading tool.
-->An Attribute is an object that represents data you want to
associate with an elements (class, methods…) in program.
--->The element to which you attach an attribute is referred to as the
target of that attribute.
Two Types:
--->Intrinsic attributes are supplied as part of the Common Language
Runtime (CLR), and they are integrated into .NET. Ex: [webmethod] ,
[serializable]…
---->Custom attributes are attributes that developer creates.
2)Attributes can be applied to
Assembly - Applied to the assembly itself
Class - Applied to instances of the class
Constructor - Applied to a given constructor
Delegate - Applied to the delegated method
Enum - Applied to an enumeration
Event - Applied to an event
Interface -Applied to an interface
Method -Applied to a method
Module - Applied to a single module
Property, Struct…….
All types
3)Attribute Decalration
Declaration:
[AttributeUsage(AttributeTargets.Class |
AttributeTargets.Constructor ,AllowMultiple = true)]
public class BugFixAttribute : System.Attribute { }
-Attribute Usage is an attribute applied to attributes: a meta-
attribute
The first argument is a set of flags that indicate the target--in this
case, the class and its constructor.
The second argument is a flag that indicates whether a given element
might receive more than one such attribute
4)Attribute Construction
public class BugFixAttribute : System.Attribute {
public BugFixAttribute(int bugID, string programmer, string date) //
Constructor
{
this.bugID = bugID;
this.programmer = programmer;
this.date = date;
}
public int BugID { //Read-Only properties
get { return bugID; }
}
public string Comment { get { return comment; } set { comment =
value; } }
}
//Note :Every attribute must have at least one constructor
5) Attribute Association
Association:
[BugFix(121, "Pradeep", "01/03/05")]
[BugFix(107, "Kumar", "01/04/05", Comment = “In MyMath class")
public class MyMath
{
//Statements
}
-The convention is to append the word Attribute to your attribute
name
[assembly: BugFix(121, "Pradeep", "01/03/05")] //Attribute
association to assembly
Note: Must place assembly attributes after all using statements and
before any code.
Attributes are placed before the element and enclosed in [ ]
6) Attributes can be accesible through Reflection
Please find the below example and comments in the program.
Example:
Suppose ,If your team organizer wants to keep track of BUG FIXES
information that contains: Id, Who had fixed this bug?, Last modified
date of particular elements(Class,method...)..Total number of bug
fixes.... in other assemblies.....
In this scenario Attributes are useful.
In the below example I have Created custom attributes and accessing
information of attribute in the same assembly....
You can try for accessing other assembly associated attributes.
using System;
using System.Collections.Generic;
using System.Text;
namespace CA_Reflection_example1
{
using System;
using System.Reflection;
using System.Diagnostics;
using System.IO;
// create custom attribute to be assigned to class members
[AttributeUsage( AttributeTargets.Class |
AttributeTargets.Method |
AttributeTargets.Property,
AllowMultiple = true)]
public class BugFix : System.Attribute
{
// **private member data
private int bugID;
private string comment;
private string date;
private string programmer;
// **attribute constructor for positional parameters
public BugFix(int bugID, string programmer, string date)
{
this.bugID = bugID;
this.programmer = programmer;
this.date = date;
}
// Read-only properties
public int BugID
{
get
{
return bugID;
}
}
// property for named parameter
public string Comment
{
get
{
return comment;
}
set
{
comment = value;
}
}
public string Date
{
get
{
return date;
}
}
public string Programmer
{
get
{
return programmer;
}
}
}
// ********* assign the attributes to the class ********
[BugFix(121, "Pradeep", "01/04/05")]
[BugFix(107, "Kumar", "01/03/05", Comment = "In Mymath class")]
public class MyMath
{
//Assign attribute to methods
[BugFix(100, "Pradeep", "04/04/04")]
public double DoFunc1(double param1)
{
return param1 + DoFunc2(param1);
}
[BugFix(101, "Kumar", "05/05/05")]
public double DoFunc2(double param1)
{
return param1 / 3;
}
public void Dofunc3()
{ }
}
[BugFix(101, "Kumar", "05/05/05")]
public class mymath1 : MyMath
{ }
public class Tester
{
public static void Main()
{
MyMath mm = new MyMath();
Console.WriteLine("Calling DoFunc(9). Result: {0}",
mm.DoFunc1(9));
// retrieve the custom attributes using Reflection
System.Reflection.MemberInfo inf = typeof(mymath1);
//Custome attributes for method
//string Current_Directory =
Directory.GetCurrentDirectory();
//Assembly a = Assembly.LoadFrom(Current_Directory +
@"\CA_Reflection_example1.exe");
//Type t = a.GetType("CA_Reflection_example1.MyMath");
//System.Reflection.MethodInfo inf =
t.GetMethod("DoFunc1");
object[] attributes;
attributes = inf.GetCustomAttributes(typeof(BugFix), true);
//attributes =
inf.GetCustomAttributes(typeof(BugFixAttribute), false);
foreach (Object attribute in attributes)
{
BugFix bfa = (BugFix)attribute;
Console.WriteLine("\nBugID: {0}", bfa.BugID);
Console.WriteLine("Programmer: {0}", bfa.Programmer);
Console.WriteLine("Date: {0}", bfa.Date);
Console.WriteLine("Comment: {0}", bfa.Comment);
Console.ReadLine();
}
Console.ReadLine();
}
}
}
On Oct 18, 10:50 am, Cerebrus <[EMAIL PROTECTED]> wrote:
> I was about to hotly contest the assertion that it was C# (as opposed
> to the CLS used for VB as well), that introduced Attributes. Then I
> found where you got your statements from :
>
> http://www.csharphelp.com/archives3/archive558.html
>
> ... and I see that the statement was picked out of context.
>
> P.S.: How's the heel healing ?
>
> On Oct 18, 7:51 am, "achilles.4k" <[EMAIL PROTECTED]> wrote:
>
>
>
> > C# introduced attributes, which allow you to embed information right
> > into the C# source code. Attributes are placed in square brackets,
> > e.g. [MTAThread], above an Attribute Target (e.g. class, field,
> > method, etcetera). C# Attributes can be used to mark fields, methods,
> > classes etcetera with markings that another program can interpret.
>
> > On Oct 16, 10:04 pm, "VIKAS GARG" <[EMAIL PROTECTED]> wrote:
>
> > > Please can anyone tell me what are attributes used for.I have gone
> > > through
> > > several tutorials
> > > but everywhere it is explained in terms of reflection
> > > that how can we retrieve information of attributes using reflection
>
> > > [System.Serializable]public class SampleClass
> > > {
> > > // Objects of this type can be serialized.
>
> > > }
>
> > > Will this make class serializable here
>
> > > after declaring attributes how do we use them- Hide quoted text -
>
> > - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
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