Статья
11/17/2011

AttributeTargets Enumeration

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Specifies the application elements on which it is valid to apply an attribute.

This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
<FlagsAttribute> _
Public Enumeration AttributeTargets

[ComVisibleAttribute(true)]
[FlagsAttribute]
public enum AttributeTargets

Members

	Member name	Description
	Assembly	Attribute can be applied to an assembly.
	Module	Attribute can be applied to a module. Note: Module refers to a portable executable file (.dll or.exe) and not a Visual Basic standard module.
	Class	Attribute can be applied to a class.
	Struct	Attribute can be applied to a structure; that is, a value type.
	Enum	Attribute can be applied to an enumeration.
	Constructor	Attribute can be applied to a constructor.
	Method	Attribute can be applied to a method.
	Property	Attribute can be applied to a property.
	Field	Attribute can be applied to a field.
	Event	Attribute can be applied to an event.
	Interface	Attribute can be applied to an interface.
	Parameter	Attribute can be applied to a parameter.
	Delegate	Attribute can be applied to a delegate.
	ReturnValue	Attribute can be applied to a return value.
	GenericParameter	Attribute can be applied to a generic parameter. Note: Currently, this attribute can be applied only in C#, Microsoft intermediate language (MSIL), and emitted code.
	All	Attribute can be applied to any application element.

Remarks

The AttributeUsageAttribute class uses this enumeration to specify the kind of element on which it is valid to apply an attribute.

AttributeTargets enumeration values can be combined with a bitwise OR operation to get the preferred combination.

Examples

The following example illustrates the application of attributes to various targets.

Note:
Visual Basic syntax currently does not support the application of attributes to type parameters.


Module DemoModule
   ' This attribute is only valid on a class.
   <AttributeUsage(AttributeTargets.Class)> _
   Public Class ClassTargetAttribute
      Inherits Attribute
   End Class

   ' This attribute is only valid on a method.
   <AttributeUsage(AttributeTargets.Method)> _
   Public Class MethodTargetAttribute
      Inherits Attribute
   End Class

   ' This attribute is only valid on a constructor.
   <AttributeUsage(AttributeTargets.Constructor)> _
   Public Class ConstructorTargetAttribute
      Inherits Attribute
   End Class

   ' This attribute is only valid on a field.
   <AttributeUsage(AttributeTargets.Field)> _
   Public Class FieldTargetAttribute
      Inherits Attribute
   End Class

   ' This attribute is valid on a class or a method.
   <AttributeUsage(AttributeTargets.Class Or AttributeTargets.Method)> _
   Public Class ClassMethodTargetAttribute
      Inherits Attribute
   End Class

   ' This attribute is valid on any target.
   <AttributeUsage(AttributeTargets.All)> _
   Public Class AllTargetsAttribute
      Inherits Attribute
   End Class

   <ClassTarget(), _
   ClassMethodTarget(), _
   AllTargets()> _
   Public Class TestClassAttribute
      <ConstructorTarget(), _
      AllTargets()> _
      Public Sub New()
      End Sub

      <MethodTarget(), _
      ClassMethodTarget(), _
      AllTargets()> _
      Public Sub Method1()
      End Sub

      <FieldTarget(), _
      AllTargets()> _
      Public myInt As Integer
   End Class

   Sub Main()
   End Sub
End Module

using System;

namespace AttTargsCS {
    // This attribute is only valid on a class.
    [AttributeUsage(AttributeTargets.Class)]
    public class ClassTargetAttribute : Attribute {
    }

    // This attribute is only valid on a method.
    [AttributeUsage(AttributeTargets.Method)]
    public class MethodTargetAttribute : Attribute {
    }

    // This attribute is only valid on a constructor.
    [AttributeUsage(AttributeTargets.Constructor)]
    public class ConstructorTargetAttribute : Attribute {
    }

    // This attribute is only valid on a field.
    [AttributeUsage(AttributeTargets.Field)]
    public class FieldTargetAttribute : Attribute {
    }

    // This attribute is valid on a class or a method.
    [AttributeUsage(AttributeTargets.Class|AttributeTargets.Method)]
    public class ClassMethodTargetAttribute : Attribute {
    }

    // This attribute is valid on a generic type parameter.
    [AttributeUsage(AttributeTargets.GenericParameter)]
    public class GenericParameterTargetAttribute : Attribute {
    }

    // This attribute is valid on any target.
    [AttributeUsage(AttributeTargets.All)]
    public class AllTargetsAttribute : Attribute {
    }

    [ClassTarget]
    [ClassMethodTarget]
    [AllTargets]
    public class TestClassAttribute {
        [ConstructorTarget]
        [AllTargets]
        TestClassAttribute() {
        }

        [MethodTarget]
        [ClassMethodTarget]
        [AllTargets]
        public void Method1() {
        }

        [FieldTarget]
        [AllTargets]
        public int myInt;

        public void GenericMethod<
            [GenericParameterTarget, AllTargets] T>(T x) {
        }

        static void Main(string[] args) {
        }
    }
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Поделиться через