When you are defining your own attribute class, you can control the manner in which it is used by placing an AttributeUsageAttribute on your attribute class. The indicated attribute class must derive from Attribute, either directly or indirectly.

Attribute classes have positional and named parameters. Each public constructor for an attribute class defines a valid sequence of positional parameters for that class. Named parameters are defined by the non-static, public, and read-write fields or properties of the attribute class.

The three properties of AttributeUsageAttribute are set by defining the following parameters:

• AttributeUsageAttribute.ValidOn

This positional parameter specifies the program elements that the indicated attribute can be placed on. The set of all possible elements that you can place an attribute on is listed in the AttributeTargets enumeration. You can combine several AttributeTargets values using a bitwise OR operation to get the desired combination of valid program elements.

• AttributeUsageAttribute.AllowMultiple

This named parameter specifies whether the indicated attribute can be specified more than once for a given program element.

• AttributeUsageAttribute.Inherited

This named parameter specifies whether the indicated attribute can be inherited by derived classes and overriding members.

For more information about using attributes, see Attribute and [<topic://cpconExtendingMetadataUsingAttributes>].

All public static members of this type are safe for multithreaded operations. No instance members are guaranteed to be thread safe.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0