AttributeUsageAttribute Class
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AttributeUsageAttribute Class

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Specifies the usage of another attribute class. This class cannot be inherited.

System.Object
  System.Attribute
    System.AttributeUsageAttribute

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

[AttributeUsageAttribute(AttributeTargets.Class, Inherited = true)]
public sealed class AttributeUsageAttribute : Attribute

The AttributeUsageAttribute type exposes the following members.

  NameDescription
Public methodAttributeUsageAttributeInitializes a new instance of the AttributeUsageAttribute class with the specified list of AttributeTargets, the AllowMultiple value, and the Inherited value.
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  NameDescription
Public propertyAllowMultipleGets or sets a Boolean value indicating whether more than one instance of the indicated attribute can be specified for a single program element.
Public propertyInheritedGets or sets a Boolean value indicating whether the indicated attribute can be inherited by derived classes and overriding members.
Public propertyValidOnGets a set of values identifying which program elements that the indicated attribute can be applied to.
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  NameDescription
Public methodEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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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:

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.

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

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.

The definition of the DispId attribute illustrates the use of a bitwise OR operation to combine several AttributeTargets values.


[AttributeUsage(AttributeTargets.Method | AttributeTargets.Field |
AttributeTargets.Property)]
public class DispIdAttribute : System.Attribute
{
  public DispIdAttribute(int value)
  {
     // . . .
  }

  public int Value
  {
     get
     {
        // . . .
        return 0;
     }
  }
}


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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