TypeFilter Delegato

Riferimento

Definizione

Spazio dei nomi:: System.Reflection

Assembly:: System.Runtime.dll

Assembly:: System.Reflection.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Importante

Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.

Filtra le classi rappresentate in una matrice di oggetti Type.

public delegate bool TypeFilter(Type ^ m, System::Object ^ filterCriteria);

public delegate bool TypeFilter(Type m, object? filterCriteria);

public delegate bool TypeFilter(Type m, object filterCriteria);

[System.Serializable]
public delegate bool TypeFilter(Type m, object filterCriteria);

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public delegate bool TypeFilter(Type m, object filterCriteria);

type TypeFilter = delegate of Type * obj -> bool

[<System.Serializable>]
type TypeFilter = delegate of Type * obj -> bool

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type TypeFilter = delegate of Type * obj -> bool

Public Delegate Function TypeFilter(m As Type, filterCriteria As Object) As Boolean

Parametri

m: Type

Oggetto Type a cui viene applicato il filtro.

filterCriteria: Object

Oggetto arbitrario usato per filtrare l'elenco.

Valore restituito

Boolean

true per includere Type nell'elenco filtrato; in caso contrario, false.

Attributi: SerializableAttribute ComVisibleAttribute

Esempio

In questo esempio viene illustrato come definire un metodo corrispondente al TypeFilter prototipo delegato che consente di usare reflection per filtrare o restituire un subset di voci corrispondenti.

Imports System.Reflection

' This interface is defined in this assembly.
Public Interface IBookRetailer
    Sub Purchase()
    Sub ApplyDiscount()
End Interface

' This interface is also defined in this assembly.
Public Interface IMusicRetailer
    Sub Purchase()
End Interface

' This class implements three interfaces;
'    Two are defined in this assembly.
'    One is defined in another assembly.
Public Class MyRetailer
    Implements IBookRetailer, IMusicRetailer, IComparable

    ' For demonstration purposes, this method returns nothing.
    Public Function CompareTo(ByVal obj As Object) As Integer Implements System.IComparable.CompareTo
        Return Nothing
    End Function

    ' For demonstration purposes only, this method does nothing.
    Public Sub ApplyDiscount() Implements IBookRetailer.ApplyDiscount
    End Sub

    ' For demonstration purposes only, this method does nothing.
    Public Sub Purchase() Implements IBookRetailer.Purchase
    End Sub

    ' For demonstration purposes only, this method does nothing.
    Public Sub Purchase1() Implements IMusicRetailer.Purchase
    End Sub
End Class

Module Module1
    Sub Main()
        ' Find the interfaces defined by the MyRetailer class. Each interface found is passed to
        ' the TypeFilter method which checks if the interface is defined in the executing assembly.
        Dim retailerType As Type = GetType(MyRetailer)
        Dim interfaces() As Type = _
            retailerType.FindInterfaces(AddressOf TypeFilter, retailerType.Assembly.GetName().ToString())

        ' Show the interfaces that are defined in this assembly that are also implemented by MyRetailer.
        Console.WriteLine("MyRetailer implements the following interfaces (defined in this assembly):")
        For Each t In interfaces
            Console.WriteLine("   {0}", t.Name)
        Next
    End Sub

    ' This method is called by the FindInterfaces method. 
    ' This method is called once per defined interface.
    Function TypeFilter(ByVal t As Type, ByVal filterCriteria As Object) As Boolean
        ' Return true if interface is defined in the same 
        ' assembly identified by the filterCriteria object.
        Return t.Assembly.GetName().ToString() = CType(filterCriteria, String)
    End Function
End Module
' The example displays the following output:
'    MyRetailer implements the following interfaces (defined in this assembly):
'      IBookRetailer
'      IMusicRetailer

Commenti

Il TypeFilter delegato viene usato per filtrare un elenco di classi. In particolare, lo si usa per filtrare le classi rappresentate in una matrice di Type oggetti. Il Type.FindInterfaces metodo usa questo delegato per filtrare l'elenco di interfacce restituite. Ogni classe derivata di Delegate e MulticastDelegate ha un costruttore e un DynamicInvoke metodo. Vedere l'esempio di codice Visual C++ specificato nella descrizione per Delegate.

Metodi di estensione

GetMethodInfo(Delegate)

Ottiene un oggetto che rappresenta il metodo rappresentato dal delegato specificato.

Si applica a