TypeFilter Delegato
Definizione
Importante
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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
true
per includere Type nell'elenco filtrato; in caso contrario, false
.
- Attributi
Esempio
In questo esempio viene illustrato come definire un metodo corrispondente al prototipo delegato TypeFilter che consente di usare la 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, viene usato 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 di Delegate
.
Metodi di estensione
GetMethodInfo(Delegate) |
Ottiene un oggetto che rappresenta il metodo rappresentato dal delegato specificato. |