IteratorStateMachineAttribute Classe

Definição

public ref class IteratorStateMachineAttribute sealed : System::Runtime::CompilerServices::StateMachineAttribute

public sealed class IteratorStateMachineAttribute : System.Runtime.CompilerServices.StateMachineAttribute

[System.AttributeUsage(System.AttributeTargets.Method, AllowMultiple=false, Inherited=false)]
public sealed class IteratorStateMachineAttribute : System.Runtime.CompilerServices.StateMachineAttribute

[System.AttributeUsage(System.AttributeTargets.Method, AllowMultiple=false, Inherited=false)]
[System.Serializable]
public sealed class IteratorStateMachineAttribute : System.Runtime.CompilerServices.StateMachineAttribute

type IteratorStateMachineAttribute = class
    inherit StateMachineAttribute

[<System.AttributeUsage(System.AttributeTargets.Method, AllowMultiple=false, Inherited=false)>]
type IteratorStateMachineAttribute = class
    inherit StateMachineAttribute

[<System.AttributeUsage(System.AttributeTargets.Method, AllowMultiple=false, Inherited=false)>]
[<System.Serializable>]
type IteratorStateMachineAttribute = class
    inherit StateMachineAttribute

Public NotInheritable Class IteratorStateMachineAttribute
Inherits StateMachineAttribute

Herança

Object

Attribute

StateMachineAttribute

IteratorStateMachineAttribute

Atributos

AttributeUsageAttribute SerializableAttribute

Exemplos

O exemplo a seguir mostra como determinar se um método é um método iterador.The following example shows how to determine whether a method is an iterator method. No exemplo, IsIteratorMethod o executa as seguintes etapas:In the example, IsIteratorMethod performs the following steps:

• Obtém um MethodInfo objeto para o nome do método usando Type.GetMethod .Obtains a MethodInfo object for the method name by using Type.GetMethod.

• Obtém um Type objeto para o atributo usando o Operador GetType.Obtains a Type object for the attribute by using GetType Operator.

• Obtém um objeto de atributo para o método e o tipo de atributo usando MethodInfo.GetCustomAttribute .Obtains an attribute object for the method and attribute type by using MethodInfo.GetCustomAttribute. Se GetCustomAttribute retorna Nothing (Visual Basic), o método não contém o atributo.If GetCustomAttribute returns Nothing (Visual Basic), the method doesn't contain the attribute.

Imports System.Collections.Generic
Imports System.Reflection
Imports System.Threading.Tasks
Imports System.Runtime.CompilerServices


Module Module1

    ' This class is used by the code below to discover method attributes.
    Public Class TheClass
        Public Async Function AsyncMethod() As Task(Of Integer)
            Await Task.Delay(5)
            Return 1
        End Function

        Public Iterator Function IteratorMethod() As IEnumerable(Of Integer)
            Yield 1
            Yield 2
        End Function

        Public Function RegularMethod() As Integer
            Return 0
        End Function
    End Class


    Private Function IsAsyncMethod(classType As Type, methodName As String)
        ' Obtain the method with the specified name.
        Dim method As MethodInfo = classType.GetMethod(methodName)

        Dim attType As Type = GetType(AsyncStateMachineAttribute)

        Dim attrib = CType(method.GetCustomAttribute(attType), AsyncStateMachineAttribute)
        ' The above variable contains the StateMachineType property.

        Return (attrib IsNot Nothing)
    End Function

    Private Function IsIteratorMethod(classType As Type, methodName As String)
        ' Obtain the method with the specified name.
        Dim method As MethodInfo = classType.GetMethod(methodName)

        Dim attType As Type = GetType(IteratorStateMachineAttribute)

        ' Obtain the custom attribute for the method.
        ' The value returned contains the StateMachineType property.
        ' Nothing is returned if the attribute isn't present for the method.
        Dim attrib = CType(method.GetCustomAttribute(attType), IteratorStateMachineAttribute)

        Return (attrib IsNot Nothing)
    End Function

    Private Sub ShowResult(classType As Type, methodName As String)
        Console.Write((methodName & ": ").PadRight(16))

        If IsAsyncMethod(classType, methodName) Then
            Console.WriteLine("Async method")
        ElseIf IsIteratorMethod(classType, methodName) Then
            Console.WriteLine("Iterator method")
        Else
            Console.WriteLine("Regular method")
        End If

        ' Note: The IteratorStateMachineAttribute applies to Visual Basic methods
        ' but not C# methods.
    End Sub

    Sub Main()
        ShowResult(GetType(TheClass), "AsyncMethod")
        ShowResult(GetType(TheClass), "IteratorMethod")
        ShowResult(GetType(TheClass), "RegularMethod")

        Console.ReadKey()
    End Sub

    '   AsyncMethod:    Async method
    '   IteratorMethod: Iterator method
    '   RegularMethod:  Regular method

End Module

Comentários

Você não deve aplicar o IteratorStateMachine atributo a métodos em seu código.You shouldn't apply the IteratorStateMachine attribute to methods in your code. Para métodos em Visual Basic que têm o modificador de iterador , o compilador aplicará o IteratorStateMachine atributo no Il que ele emitir.For methods in Visual Basic that have the Iterator modifier, the compiler will apply the IteratorStateMachine attribute in the IL that it emits.

Quando um método ( MethodName ) em Visual Basic tem o Iterator modificador, o compilador emite Il que inclui uma estrutura de máquina de estado.When a method ( MethodName ) in Visual Basic has the Iterator modifier, the compiler emits IL that includes a state machine structure. Essa estrutura contém o código no método.That structure contains the code in the method. Esse IL também contém um método stub ( MethodName ) que chama para o computador de estado.That IL also contains a stub method ( MethodName ) that calls into the state machine. O compilador adiciona o IteratorStateMachine atributo ao método de stub para que as ferramentas possam identificar o computador de estado correspondente.The compiler adds the IteratorStateMachine attribute to the stub method so that tools can identify the corresponding state machine. Os detalhes do IL emitido podem ser alterados em versões futuras dos compiladores.Details of the emitted IL might change in future releases of the compilers.

Um método iterador executa uma iteração personalizada em uma coleção usando a Yield instrução (Visual Basic) para retornar cada elemento um de cada vez.An iterator method performs a custom iteration over a collection by using the Yield (Visual Basic) statement to return each element one at a time. Para obter mais informações, consulte Iteradores.For more information, see Iterators.

Construtores

Propriedades

Métodos

Implantações explícitas de interface

Aplica-se a

Confira também

• AsyncStateMachineAttribute
• StateMachineType