Attribute Klasse

Definition

public ref class Attribute abstract

public ref class Attribute abstract : System::Runtime::InteropServices::_Attribute

[System.AttributeUsage(System.AttributeTargets.All, AllowMultiple=false, Inherited=true)]
public abstract class Attribute

[System.AttributeUsage(System.AttributeTargets.All, AllowMultiple=false, Inherited=true)]
[System.Runtime.InteropServices.ClassInterface(System.Runtime.InteropServices.ClassInterfaceType.None)]
[System.Serializable]
public abstract class Attribute : System.Runtime.InteropServices._Attribute

[System.AttributeUsage(System.AttributeTargets.All, AllowMultiple=false, Inherited=true)]
[System.Runtime.InteropServices.ClassInterface(System.Runtime.InteropServices.ClassInterfaceType.None)]
[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public abstract class Attribute : System.Runtime.InteropServices._Attribute

[<System.AttributeUsage(System.AttributeTargets.All, AllowMultiple=false, Inherited=true)>]
type Attribute = class

[<System.AttributeUsage(System.AttributeTargets.All, AllowMultiple=false, Inherited=true)>]
[<System.Runtime.InteropServices.ClassInterface(System.Runtime.InteropServices.ClassInterfaceType.None)>]
[<System.Serializable>]
type Attribute = class
    interface _Attribute

[<System.AttributeUsage(System.AttributeTargets.All, AllowMultiple=false, Inherited=true)>]
[<System.Runtime.InteropServices.ClassInterface(System.Runtime.InteropServices.ClassInterfaceType.None)>]
[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type Attribute = class
    interface _Attribute

Public MustInherit Class Attribute

Public MustInherit Class Attribute
Implements _Attribute

Vererbung

Object

Attribute

Abgeleitet

Microsoft.Extensions.Compliance.Classification.DataClassificationAttribute

Microsoft.Extensions.Configuration.ConfigurationKeyNameAttribute

Microsoft.Extensions.Configuration.UserSecrets.UserSecretsIdAttribute

Microsoft.Extensions.DependencyInjection.ActivatorUtilitiesConstructorAttribute

Microsoft.Extensions.DependencyInjection.FromKeyedServicesAttribute

Mehr …

Attribute

AttributeUsageAttribute ClassInterfaceAttribute SerializableAttribute ComVisibleAttribute

Implementiert

_Attribute

Beispiele

Im folgenden Codebeispiel wird die Verwendung von Attributeveranschaulicht.

using namespace System;
using namespace System::Reflection;

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

// A custom attribute to allow a target to have a pet.
public ref class AnimalTypeAttribute: public Attribute
{
public:

    // The constructor is called when the attribute is set.
    AnimalTypeAttribute( Animal pet )
    {
        thePet = pet;
    }


protected:

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

public:

    property Animal Pet 
    {
        // .. and show a copy to the outside world.
        Animal get()
        {
            return thePet;
        }

        void set( Animal value )
        {
            thePet = value;
        }
    }
};

// A test class where each method has its own pet.
ref class AnimalTypeTestClass
{
public:

    [AnimalType(Animal::Dog)]
    void DogMethod(){}


    [AnimalType(Animal::Cat)]
    void CatMethod(){}

    [AnimalType(Animal::Bird)]
    void BirdMethod(){}

};

int main()
{
    AnimalTypeTestClass^ testClass = gcnew AnimalTypeTestClass;
    Type^ type = testClass->GetType();

    // Iterate through all the methods of the class.
    System::Collections::IEnumerator^ myEnum = 
        type->GetMethods()->GetEnumerator();
    while ( myEnum->MoveNext() )
    {
        MethodInfo^ mInfo = safe_cast<MethodInfo^>(myEnum->Current);

        // Iterate through all the Attributes for each method.
        System::Collections::IEnumerator^ myEnum1 = 
            Attribute::GetCustomAttributes( mInfo )->GetEnumerator();
        while ( myEnum1->MoveNext() )
        {
            Attribute^ attr = safe_cast<Attribute^>(myEnum1->Current);

            // Check for the AnimalType attribute.
            if ( attr->GetType() == AnimalTypeAttribute::typeid )
                Console::WriteLine( "Method {0} has a pet {1} attribute.", 
                mInfo->Name, (dynamic_cast<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.
 */

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.
 */

open System

// An enumeration of animals. Start at 1 (0 = uninitialized).
type Animal =
    | Dog = 1
    | Cat = 2
    | Bird = 3

// A custom attribute to allow a target to have a pet.
type AnimalTypeAttribute(pet) =
    inherit Attribute()
    member val Pet = pet with get, set

// A test class where each method has its own pet.
type AnimalTypeTestClass() =
    [<AnimalType(Animal.Dog)>]
    member _.DogMethod() = ()

    [<AnimalType(Animal.Cat)>]
    member _.CatMethod() = ()

    [<AnimalType(Animal.Bird)>]
    member _.BirdMethod() = ()

let testClass = AnimalTypeTestClass()
let clsType = testClass.GetType()
// Iterate through all the methods of the class.
for mInfo in clsType.GetMethods() do
    // Iterate through all the Attributes for each method.
    for attr in Attribute.GetCustomAttributes mInfo do
        // Check for the AnimalType attribute.
        if attr.GetType() = typeof<AnimalTypeAttribute> then
            printfn $"Method {mInfo.Name} has a pet {(attr :?> AnimalTypeAttribute).Pet} attribute."

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

Imports System.Reflection

Public Module CustomAttrVB

    ' An enumeration of animals. Start at 1 (0 = uninitialized).
    Public Enum Animal
        ' Pets
        Dog = 1
        Cat
        Bird
    End Enum

    ' Visual Basic requires the AttributeUsage be specified.
    ' A custom attribute to allow a target to have a pet.
    <AttributeUsage(AttributeTargets.Method)> _
    Public Class AnimalTypeAttribute
        Inherits Attribute

        ' The constructor is called when the attribute is set.
        Public Sub New(ByVal animal As Animal)
            Me.thePet = animal
        End Sub

        ' Keep a variable internally ...
        Protected thePet As Animal

        ' .. and show a copy to the outside world.
        Public Property Pet() As Animal
            Get
                Return thePet
            End Get
            Set(ByVal Value As Animal)
                thePet = Value
            End Set
        End Property

    End Class

    ' A test class where each method has its own pet.
    Class AnimalTypeTestClass

        <AnimalType(Animal.Dog)> _
        Public Sub DogMethod()
        End Sub

        <AnimalType(Animal.Cat)> _
        Public Sub CatMethod()
        End Sub

        <AnimalType(Animal.Bird)> _
        Public Sub BirdMethod()
        End Sub
    End Class

    ' The runtime test.
    Sub Main()
        Dim testClass As New AnimalTypeTestClass()
        Dim tcType As Type = testClass.GetType()
        Dim mInfo As MethodInfo
        ' Iterate through all the methods of the class.
        For Each mInfo In tcType.GetMethods()
            Dim attr As Attribute
            ' Iterate through all the attributes of the method.
            For Each attr In Attribute.GetCustomAttributes(mInfo)
                If TypeOf attr Is AnimalTypeAttribute Then
                    Dim attrCustom As AnimalTypeAttribute = _
                        CType(attr, AnimalTypeAttribute)
                    Console.WriteLine("Method {0} has a pet {1} attribute.", _
                         mInfo.Name(), attrCustom.Pet.ToString())
                End If
            Next
        Next
    End Sub
End Module

' Output:
' Method DogMethod has a pet Dog attribute.
' Method CatMethod has a pet Cat attribute.
' Method BirdMethod has a pet Bird attribute.

Hinweise

Die Attribute Klasse ordnet vordefinierte Systeminformationen oder benutzerdefinierte Informationen einem Zielelement zu. Ein Zielelement kann eine Assembly, Klasse, Konstruktor, Delegate, Enumeration, Ereignis, Feld, Schnittstelle, Methode, portable ausführbare Dateimodul, Parameter, Eigenschaft, Rückgabewert, Struktur oder ein anderes Attribut sein.

Informationen, die von einem Attribut bereitgestellt werden, werden auch als Metadaten bezeichnet. Metadaten können zur Laufzeit von Ihrer Anwendung untersucht werden, um zu steuern, wie Ihr Programm Daten verarbeitet, oder vor der Laufzeit durch externe Tools, um zu steuern, wie Ihre Anwendung selbst verarbeitet oder verwaltet wird. Beispiel: .NET vordefinierte und verwendet Attributtypen, um das Laufzeitverhalten zu steuern, und einige Programmiersprachen verwenden Attributtypen, um Sprachfeatures darzustellen, die vom allgemeinen .NET-Typsystem nicht direkt unterstützt werden.

Alle Attributtypen werden direkt oder indirekt von der Attribute Klasse abgeleitet. Attribute können auf jedes Zielelement angewendet werden; Mehrere Attribute können auf dasselbe Zielelement angewendet werden. und Attribute können von einem Element geerbt werden, das von einem Zielelement abgeleitet wurde. Verwenden Sie die AttributeTargets Klasse, um das Zielelement anzugeben, auf das das Attribut angewendet wird.

Die Attribute Klasse bietet praktische Methoden zum Abrufen und Testen von benutzerdefinierten Attributen. Weitere Informationen zur Verwendung von Attributen finden Sie unter Anwenden von Attributen und Attribute.

Konstruktoren

Eigenschaften

Methoden

Explizite Schnittstellenimplementierungen

Gilt für:

Threadsicherheit

Dieser Typ ist threadsicher.

Weitere Informationen

• Anwenden von Attributen
• Erweitern von Metadaten mithilfe von Attributen