Propriedade declaração

Declares the name of a property, and the property procedures used to store and retrieve the value of the property.

[ <attributelist> ] [ Default ] [ accessmodifier ] 
[ propertymodifiers ] [ Shared ] [ Shadows ] [ ReadOnly | WriteOnly ] 
Property name ( [ parameterlist ] ) [ As returntype ] [ Implements implementslist ]
    [ <attributelist> ] [ accessmodifier ] Get
        [ statements ]
    End Get
    [ <attributelist> ] [ accessmodifier ] Set ( ByVal value As returntype [, parameterlist ] )
        [ statements ]
    End Set
End Property
- or -
[ <attributelist> ] [ Default ] [ accessmodifier ] 
[ propertymodifiers ] [ Shared ] [ Shadows ] [ ReadOnly | WriteOnly ] 
Property name ( [ parameterlist ] ) [ As returntype ] [ Implements implementslist ]

Parts

Comentários

The Property statement introduces the declaration of a property. A property can have a Get procedure (read only), a Set procedure (write only), or both (read-write). Você pode omitir o Get e Setprocedimento ao usar uma propriedadede auto-implementado. For more information, see Propriedades autoimplementadas (Visual Basic).

Você pode usar Property somente no nível de classe . This means the declaration context for a property must be a class, structure, module, or interface, and cannot be a source file, namespace, procedure, or block. For more information, see Contextos de declaração e níveis de acesso padrão (Visual Basic).

By default, properties use public access. You can adjust a property's access level with an access modifier on the Property statement, and you can optionally adjust one of its property procedures to a more restrictive access level.

Visual Basic passes a parameter to the Set procedure during property assignments. If you do not supply a parameter for Set, the integrated development environment (IDE) uses an implicit parameter named value. This parameter holds the value to be assigned to the property. You typically store this value in a private local variable and return it whenever the Get procedure is called.

Rules

• Mixed Access Levels. Se você estiver definindo uma leitura-gravar a propriedade, opcionalmente, você pode especificar outro nível de acesso para qualquer um de Get ou o Set procedimento, mas não ambos. If you do this, the procedure access level must be more restrictive than the property's access level. For example, if the property is declared Friend, you can declare the Set procedure Private, but not Public.

  If you are defining a ReadOnly or WriteOnly property, the single property procedure (Get or Set, respectively) represents all of the property. You cannot declare a different access level for such a procedure, because that would set two access levels for the property.

• Return Type. O Propertydedemonstrativo pode declarar o tipo de dados de que o valor retornado. You can specify any data type or the name of an enumeration, structure, class, or interface.

  If you do not specify returntype, the property returns Object.

• Implementação. Se esta propriedade usa a Implementspalavra-chave, o que contém uma classe ou estrutura deve ter um Implementsademonstrativo imediatamente seguinte sua Class ou Structuredemonstrativo. The Implements statement must include each interface specified in implementslist. However, the name by which an interface defines the Property (in definedname) does not have to be the same as the name of this property (in name).

Behavior

• Returning from a Property Procedure. Quando o Get ou Set procedimento retorna para o código de chamada, a execução continua com a demonstrativo após a demonstrativo que invocou o proprietário.

  The Exit Property and Return statements cause an immediate exit from a property procedure. Any number of Exit Property and Return statements can appear anywhere in the procedure, and you can mix Exit Property and Return statements.

• Valorde retorno. Para retornar um valor de um Get procedimento, você pode atribuir o valor do nome de propriedade -lo ou incluí-lo em um Return demonstrativo. The following example assigns the return value to the property name quoteForTheDay and then uses the Exit Property statement to return.

  Private quoteValue As String = "No quote assigned yet."
  

  ReadOnly Property quoteForTheDay() As String
      Get
          quoteForTheDay = quoteValue
          Exit Property
      End Get
  End Property
  

  If you use Exit Property without assigning a value to name, the Get procedure returns the default value for the property's data type.

  The Return statement at the same time assigns the Get procedure return value and exits the procedure. The following example shows this.

  Private quoteValue As String = "No quote assigned yet."
  

  ReadOnly Property quoteForTheDay() As String
      Get
          Return quoteValue
      End Get
  End Property
  

Exemplo

The following example declares a property in a class.

Class Class1
    ' Define a local variable to store the property value.
    Private propertyValue As String
    ' Define the property.
    Public Property prop1() As String
        Get
            ' The Get property procedure is called when the value
            ' of a property is retrieved.
            Return propertyValue
        End Get
        Set(ByVal value As String)
            ' The Set property procedure is called when the value 
            ' of a property is modified.  The value to be assigned
            ' is passed in the argument to Set.
            propertyValue = value
        End Set
    End Property
End Class

Consulte também

Referência

Declaração Get

Declaração Set (Visual Basic)

Lista de parâmetros (Visual Basic)

Padrão (Visual Basic)

Conceitos

Propriedades autoimplementadas (Visual Basic)

Outros recursos

Objetos e Classes no Visual Basic