Attribute.IsDefaultAttribute Méthode

Définition

En cas de substitution dans une classe dérivée, indique si la valeur de cette instance est la valeur par défaut pour la classe dérivée.When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.

public:
 virtual bool IsDefaultAttribute();
public virtual bool IsDefaultAttribute ();
abstract member IsDefaultAttribute : unit -> bool
override this.IsDefaultAttribute : unit -> bool
Public Overridable Function IsDefaultAttribute () As Boolean

Retours

true si cette instance est l’attribut par défaut de la classe ; sinon, false.true if this instance is the default attribute for the class; otherwise, false.

Exemples

L’exemple de code suivant illustre l’utilisation de IsDefaultAttribute.The following code example illustrates the use of IsDefaultAttribute.

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;
   }

   // Provide a default constructor and make Dog the default.
   AnimalTypeAttribute()
   {
      thePet = Animal::Dog;
   }

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;
      }

   }

   // Override IsDefaultAttribute to return the correct response.
   virtual bool IsDefaultAttribute() override
   {
      return thePet == Animal::Dog;
   }
};

public ref class TestClass
{
public:

   // Use the default constructor.

   [AnimalType]
   void Method1(){}
};

int main()
{
   // Get the class type to access its metadata.
   Type^ clsType = TestClass::typeid;

   // Get type information for the method.
   MethodInfo^ mInfo = clsType->GetMethod( "Method1" );

   // Get the AnimalType attribute for the method.
   AnimalTypeAttribute^ atAttr = dynamic_cast<AnimalTypeAttribute^>(Attribute::GetCustomAttribute( mInfo, AnimalTypeAttribute::typeid ));

   // Check to see if the default attribute is applied.
   Console::WriteLine( "The attribute {0} for method {1} in class {2}", atAttr->Pet, mInfo->Name, clsType->Name );
   Console::WriteLine( "{0} the default for the AnimalType attribute.", atAttr->IsDefaultAttribute() ? (String^)"is" : "is not" );
}
using System;
using System.Reflection;

namespace DefAttrCS 
{
    // 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;
        }

        // Provide a default constructor and make Dog the default.
        public AnimalTypeAttribute() 
        {
            thePet = Animal.Dog;
        }

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

        // .. and show a copy to the outside world.
        public Animal Pet 
        {
            get { return thePet; }
            set { thePet = Pet; }
        }

        // Override IsDefaultAttribute to return the correct response.
        public override bool IsDefaultAttribute() 
        {
            if (thePet == Animal.Dog)
                return true;

            return false;
        }
    }

    public class TestClass 
    {
        // Use the default constructor.
        [AnimalType]
        public void Method1()
        {}
    }

    class DemoClass 
    {
        static void Main(string[] args) 
        {
            // Get the class type to access its metadata.
            Type clsType = typeof(TestClass);
            // Get type information for the method.
            MethodInfo mInfo = clsType.GetMethod("Method1");
            // Get the AnimalType attribute for the method.
            AnimalTypeAttribute atAttr = 
                (AnimalTypeAttribute)Attribute.GetCustomAttribute(mInfo,
                typeof(AnimalTypeAttribute));
            // Check to see if the default attribute is applied.
            Console.WriteLine("The attribute {0} for method {1} in class {2}",
                atAttr.Pet, mInfo.Name, clsType.Name); 
            Console.WriteLine("{0} the default for the AnimalType attribute.", 
                atAttr.IsDefaultAttribute() ? "is" : "is not");
        }
    }
}
Imports System.Reflection

Module DemoModule

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

    ' Visual Basic requires that 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

        ' Provide a default constructor and make Dog the default.
        Public Sub New()
            thePet = Animal.Dog
        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

        ' Override IsDefaultAttribute to return the correct response.
        Public Overrides Function IsDefaultAttribute() As Boolean
            If thePet = Animal.Dog Then
                Return True
            Else
                Return False
            End If
        End Function

    End Class

    Public Class TestClass
        ' Use the default constructor.
        <AnimalType()> _
        Public Sub Method1()
        End Sub

    End Class

    Sub Main()
        ' Get the class type to access its metadata.
        Dim clsType As Type = GetType(TestClass)
        ' Get type information for the method.
        Dim mInfo As MethodInfo = clsType.GetMethod("Method1")
        ' Get the AnimalType attribute for the method.
        Dim attr As Attribute = Attribute.GetCustomAttribute(mInfo, _
            GetType(AnimalTypeAttribute))
        If Not attr Is Nothing And TypeOf attr Is AnimalTypeAttribute Then
            ' Convert the attribute to the required type.
            Dim atAttr As AnimalTypeAttribute = _
                CType(attr, AnimalTypeAttribute)
            Dim strDef As String
            ' Check to see if the default attribute is applied.
            If atAttr.IsDefaultAttribute() Then
                strDef = "is"
            Else
                strDef = "is not"
            End If
            ' Display the result.
            Console.WriteLine("The attribute {0} for method {1} " & _
                    "in class {2}", atAttr.Pet.ToString(), mInfo.Name, _
                    clsType.Name)
            Console.WriteLine("{0} the default for the AnimalType " & _
                    "attribute.", strDef)
        End If
    End Sub
End Module

Remarques

L’implémentation par défaut de cette classe retourne false et doit être implémentée dans la classe dérivée pour être utile à cette classe.The default implementation of this class returns false, and must be implemented in the derived class to be useful to that class.

L’implémentation de cette méthode dans une classe dérivée compare la valeur de cette instance à une valeur par défaut standard, puis retourne une valeur booléenne qui indique si la valeur de cette instance est égale à la valeur standard.The implementation of this method in a derived class compares the value of this instance to a standard default value, then returns a Boolean value that indicates whether the value of this instance is equal to the standard value. La valeur standard est généralement codée comme une constante dans l’implémentation, ou stockée par programme dans un champ utilisé par l’implémentation.The standard value is typically coded as a constant in the implementation, or stored programmatically in a field used by the implementation.

S’applique à