This is the base class for all
custom attributes. Attributes are the
.NET programmer's means of inserting additional
metadata into a type's definition. For example, the
.NET Serialization mechanism uses an attribute to indicate which
fields in a type should not be serialized (see the
System.Reflection.FieldAttributes.NotSerialized
enumeration value). .NET programmers are free to create their own
attributes (called custom attributes, although
from a certain perspective all attributes are inherently custom) by
creating a new type that claims Attribute as its
base class type.
By themselves, attributes offer no modification to a
type's behavioral semantics; that is, attributes
don't modify the type's methods or
execution in any way. In fact, attribute instances
aren't even created until they are retrieved out of
the type's metadata via the Reflection APIs. The
entire purpose of an attribute is to act as a marker inside the
type's metadata for consumption by some other API,
library, or facility. For example, the Serialization APIs in the .NET
Framework Class Library use the Serializable
attribute to indicate which types are serializable. However, by
themselves, the attributes carry no code to perform the actual act of
serialization. This must be done by passing the instance of the type
into instances of the Serialization classes, in which the attribute
is retrieved and examined, and
"appropriate" action is taken.
Attributes can be attached to any metadata component in the .NET
system. This means fields, methods, properties, events, types
(classes and value types), assemblies, modules, and more can all be
the target of attribute declarations. (An attribute indicates which
types it is restricted to by using the
AttributeTargets enumeration.)
The base Attribute class provides helper functions
for testing custom attributes, including the IsDefined(
) method, which examines a code element and indicates
whether its metadata is decorated with a specified type of attribute.
To use this method, you must provide the element using the
appropriate reflection type (e.g.,
System.Reflection.Assembly or
System.Reflection.ParameterInfo). You can also use
the GetCustomAttribute( ) method to get a
reference to an attribute of a specified type, or the
GetCustomAttributes( ) method to get an array that
contains all matching attributes. When applied to a class or class
member, these methods consider all ancestors. To disable this default
behavior, use one of the overloaded methods that allows you to supply
the inherit parameter, and set it to
false.
Custom attributes should override the TypeId
property so that it supplies a user-defined identifier that uniquely
describes the instance of this attribute on the type. This is
entirely because more than one instance of an attribute can be
associated with any particular metadata-token (field, type,
parameter, and so on) instance.
public abstract class Attribute {
// Protected Constructors
protected Attribute( );
// Public Instance Properties
public virtual object TypeId{get; }
// Public Static Methods
public static Attribute GetCustomAttribute(System.Reflection.Assembly element,
Type attributeType);
public static Attribute GetCustomAttribute(System.Reflection.Assembly element,
Type attributeType, bool inherit);
public static Attribute GetCustomAttribute(System.Reflection.MemberInfo element,
Type attributeType);
public static Attribute GetCustomAttribute(System.Reflection.MemberInfo element,
Type attributeType, bool inherit);
public static Attribute GetCustomAttribute(System.Reflection.Module element,
Type attributeType);
public static Attribute GetCustomAttribute(System.Reflection.Module element,
Type attributeType, bool inherit);
public static Attribute GetCustomAttribute(System.Reflection.ParameterInfo element,
Type attributeType);
public static Attribute GetCustomAttribute(System.Reflection.ParameterInfo element,
Type attributeType, bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Assembly element);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Assembly element,
bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Assembly element,
Type attributeType);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Assembly element,
Type attributeType, bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.MemberInfo element);
public static Attribute[ ] GetCustomAttributes(System.Reflection.MemberInfo element,
bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.MemberInfo element,
Type type);
public static Attribute[ ] GetCustomAttributes(System.Reflection.MemberInfo element,
Type type, bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Module element);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Module element,
bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Module element,
Type attributeType);
public static Attribute[ ] GetCustomAttributes(System.Reflection.Module element,
Type attributeType, bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.ParameterInfo element);
public static Attribute[ ] GetCustomAttributes(System.Reflection.ParameterInfo element,
bool inherit);
public static Attribute[ ] GetCustomAttributes(System.Reflection.ParameterInfo element,
Type attributeType);
public static Attribute[ ] GetCustomAttributes(System.Reflection.ParameterInfo element,
Type attributeType, bool inherit);
public static bool IsDefined(System.Reflection.Assembly element, Type attributeType);
public static bool IsDefined(System.Reflection.Assembly element, Type attributeType, bool inherit);
public static bool IsDefined(System.Reflection.MemberInfo element, Type attributeType);
public static bool IsDefined(System.Reflection.MemberInfo element, Type attributeType, bool inherit);
public static bool IsDefined(System.Reflection.Module element, Type attributeType);
public static bool IsDefined(System.Reflection.Module element, Type attributeType, bool inherit);
public static bool IsDefined(System.Reflection.ParameterInfo element, Type attributeType);
public static bool IsDefined(System.Reflection.ParameterInfo element, Type attributeType, bool inherit);
// Public Instance Methods
public override bool Equals(object obj);
// overrides object
public override int GetHashCode( );
// overrides object
public virtual bool IsDefaultAttribute( );
public virtual bool Match(object obj);
}
