This documentation is archived and is not being maintained.

Recommended Version

Attribute Class

Visual Studio 2010

Other Versions

Represents the base class for custom attributes.

Inheritance Hierarchy

System.Object
System.Attribute
More...

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

C++

[SerializableAttribute]
[ClassInterfaceAttribute(ClassInterfaceType.None)]
[ComVisibleAttribute(true)]
[AttributeUsageAttribute(AttributeTargets.All, Inherited = true, AllowMultiple = false)]
public abstract class Attribute : _Attribute

The Attribute type exposes the following members.

	Name	Description
	Attribute	Initializes a new instance of the Attribute class.

	Name	Description
	TypeId	When implemented in a derived class, gets a unique identifier for this Attribute.

	Name	Description
	Equals	Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Overrides Object.Equals(Object).)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetCustomAttribute(Assembly, Type)	Retrieves a custom attribute applied to a specified assembly. Parameters specify the assembly and the type of the custom attribute to search for.
	GetCustomAttribute(MemberInfo, Type)	Retrieves a custom attribute applied to a member of a type. Parameters specify the member, and the type of the custom attribute to search for.
	GetCustomAttribute(Module, Type)	Retrieves a custom attribute applied to a module. Parameters specify the module, and the type of the custom attribute to search for.
	GetCustomAttribute(ParameterInfo, Type)	Retrieves a custom attribute applied to a method parameter. Parameters specify the method parameter, and the type of the custom attribute to search for.
	GetCustomAttribute(Assembly, Type, Boolean)	Retrieves a custom attribute applied to an assembly. Parameters specify the assembly, the type of the custom attribute to search for, and an ignored search option.
	GetCustomAttribute(MemberInfo, Type, Boolean)	Retrieves a custom attribute applied to a member of a type. Parameters specify the member, the type of the custom attribute to search for, and whether to search ancestors of the member.
	GetCustomAttribute(Module, Type, Boolean)	Retrieves a custom attribute applied to a module. Parameters specify the module, the type of the custom attribute to search for, and an ignored search option.
	GetCustomAttribute(ParameterInfo, Type, Boolean)	Retrieves a custom attribute applied to a method parameter. Parameters specify the method parameter, the type of the custom attribute to search for, and whether to search ancestors of the method parameter.
	GetCustomAttributes(Assembly)	Retrieves an array of the custom attributes applied to an assembly. A parameter specifies the assembly.
	GetCustomAttributes(MemberInfo)	Retrieves an array of the custom attributes applied to a member of a type. A parameter specifies the member.
	GetCustomAttributes(Module)	Retrieves an array of the custom attributes applied to a module. A parameter specifies the module.
	GetCustomAttributes(ParameterInfo)	Retrieves an array of the custom attributes applied to a method parameter. A parameter specifies the method parameter.
	GetCustomAttributes(Assembly, Boolean)	Retrieves an array of the custom attributes applied to an assembly. Parameters specify the assembly, and an ignored search option.
	GetCustomAttributes(Assembly, Type)	Retrieves an array of the custom attributes applied to an assembly. Parameters specify the assembly, and the type of the custom attribute to search for.
	GetCustomAttributes(MemberInfo, Boolean)	Retrieves an array of the custom attributes applied to a member of a type. Parameters specify the member, the type of the custom attribute to search for, and whether to search ancestors of the member.
	GetCustomAttributes(MemberInfo, Type)	Retrieves an array of the custom attributes applied to a member of a type. Parameters specify the member, and the type of the custom attribute to search for.
	GetCustomAttributes(Module, Boolean)	Retrieves an array of the custom attributes applied to a module. Parameters specify the module, and an ignored search option.
	GetCustomAttributes(Module, Type)	Retrieves an array of the custom attributes applied to a module. Parameters specify the module, and the type of the custom attribute to search for.
	GetCustomAttributes(ParameterInfo, Boolean)	Retrieves an array of the custom attributes applied to a method parameter. Parameters specify the method parameter, and whether to search ancestors of the method parameter.
	GetCustomAttributes(ParameterInfo, Type)	Retrieves an array of the custom attributes applied to a method parameter. Parameters specify the method parameter, and the type of the custom attribute to search for.
	GetCustomAttributes(Assembly, Type, Boolean)	Retrieves an array of the custom attributes applied to an assembly. Parameters specify the assembly, the type of the custom attribute to search for, and an ignored search option.
	GetCustomAttributes(MemberInfo, Type, Boolean)	Retrieves an array of the custom attributes applied to a member of a type. Parameters specify the member, the type of the custom attribute to search for, and whether to search ancestors of the member.
	GetCustomAttributes(Module, Type, Boolean)	Retrieves an array of the custom attributes applied to a module. Parameters specify the module, the type of the custom attribute to search for, and an ignored search option.
	GetCustomAttributes(ParameterInfo, Type, Boolean)	Retrieves an array of the custom attributes applied to a method parameter. Parameters specify the method parameter, the type of the custom attribute to search for, and whether to search ancestors of the method parameter.
	GetHashCode	Returns the hash code for this instance. (Overrides Object.GetHashCode().)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	IsDefaultAttribute	When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.
	IsDefined(Assembly, Type)	Determines whether any custom attributes are applied to an assembly. Parameters specify the assembly, and the type of the custom attribute to search for.
	IsDefined(MemberInfo, Type)	Determines whether any custom attributes are applied to a member of a type. Parameters specify the member, and the type of the custom attribute to search for.
	IsDefined(Module, Type)	Determines whether any custom attributes of a specified type are applied to a module. Parameters specify the module, and the type of the custom attribute to search for.
	IsDefined(ParameterInfo, Type)	Determines whether any custom attributes are applied to a method parameter. Parameters specify the method parameter, and the type of the custom attribute to search for.
	IsDefined(Assembly, Type, Boolean)	Determines whether any custom attributes are applied to an assembly. Parameters specify the assembly, the type of the custom attribute to search for, and an ignored search option.
	IsDefined(MemberInfo, Type, Boolean)	Determines whether any custom attributes are applied to a member of a type. Parameters specify the member, the type of the custom attribute to search for, and whether to search ancestors of the member.
	IsDefined(Module, Type, Boolean)	Determines whether any custom attributes are applied to a module. Parameters specify the module, the type of the custom attribute to search for, and an ignored search option.
	IsDefined(ParameterInfo, Type, Boolean)	Determines whether any custom attributes are applied to a method parameter. Parameters specify the method parameter, the type of the custom attribute to search for, and whether to search ancestors of the method parameter.
	Match	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

Explicit Interface Implementations

	Name	Description
	_Attribute.GetIDsOfNames	Maps a set of names to a corresponding set of dispatch identifiers.
	_Attribute.GetTypeInfo	Retrieves the type information for an object, which can be used to get the type information for an interface.
	_Attribute.GetTypeInfoCount	Retrieves the number of type information interfaces that an object provides (either 0 or 1).
	_Attribute.Invoke	Provides access to properties and methods exposed by an object.

Top

The Attribute class associates predefined system information or user-defined custom information with a target element. A target element can be an assembly, class, constructor, delegate, enum, event, field, interface, method, portable executable file module, parameter, property, return value, struct, or another attribute.

Information provided by an attribute is also known as metadata. Metadata can be examined at run time by your application to control how your program processes data, or before run time by external tools to control how your application itself is processed or maintained. For example, the .NET Framework predefines and uses attribute types to control run-time behavior, and some programming languages use attribute types to represent language features not directly supported by the .NET Framework common type system.

All attribute types derive directly or indirectly from the Attribute class. Attributes can be applied to any target element; multiple attributes can be applied to the same target element; and attributes can be inherited by an element derived from a target element. Use the AttributeTargets class to specify the target element to which the attribute is applied.

The Attribute class provides convenient methods to retrieve and test custom attributes. For more information about using attributes, see Applying Attributes and Extending Metadata Using Attributes.

Examples

The following code example demonstrates the usage of Attribute.

C++


using System;
using System.Reflection;

// An enumeration of animals. Start at 1 (0 = uninitialized).
public enum Animal {
    // Pets.
    Dog = 1,
    Cat,
    Bird,
}

// A custom attribute to allow a target to have a pet.
public class AnimalTypeAttribute : Attribute {
    // The constructor is called when the attribute is set.
    public AnimalTypeAttribute(Animal pet) {
        thePet = pet;
    }

    // Keep a variable internally ...
    protected Animal thePet;

    // .. and show a copy to the outside world.
    public Animal Pet {
        get { return thePet; }
        set { thePet = value; }
    }
}

// A test class where each method has its own pet.
class AnimalTypeTestClass {
    [AnimalType(Animal.Dog)]
    public void DogMethod() {}

    [AnimalType(Animal.Cat)]
    public void CatMethod() {}

    [AnimalType(Animal.Bird)]
    public void BirdMethod() {}
}

class DemoClass {
    static void Main(string[] args) {
        AnimalTypeTestClass testClass = new AnimalTypeTestClass();
        Type type = testClass.GetType();
        // Iterate through all the methods of the class.
        foreach(MethodInfo mInfo in type.GetMethods()) {
            // Iterate through all the Attributes for each method.
            foreach (Attribute attr in
                Attribute.GetCustomAttributes(mInfo)) {
                // Check for the AnimalType attribute.
                if (attr.GetType() == typeof(AnimalTypeAttribute))
                    Console.WriteLine(
                        "Method {0} has a pet {1} attribute.",
                        mInfo.Name, ((AnimalTypeAttribute)attr).Pet);
            }

        }
    }
}
/*
 * Output:
 * Method DogMethod has a pet Dog attribute.
 * Method CatMethod has a pet Cat attribute.
 * Method BirdMethod has a pet Bird attribute.
 */

Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Attribute Class

Inheritance Hierarchy

Syntax

Constructors

Properties

Methods

Explicit Interface Implementations

Remarks

Examples

Version Information

.NET Framework

.NET Framework Client Profile

Portable Class Library

Platforms

Thread Safety

See Also

Reference

Other Resources

Inheritance Hierarchy