Type.IsAssignableFrom(Type) Yöntem

Tanım

Ad Alanı:

System

Bütünleştirilmiş Kod:

System.Runtime.dll

Bütünleştirilmiş Kod:

netstandard.dll

Bütünleştirilmiş Kod:

mscorlib.dll

Belirtilen türde bir örneğin c geçerli türdeki bir değişkene atanıp atanamayacağını belirler.

public:
 virtual bool IsAssignableFrom(Type ^ c);

public virtual bool IsAssignableFrom (Type? c);

public virtual bool IsAssignableFrom (Type c);

abstract member IsAssignableFrom : Type -> bool
override this.IsAssignableFrom : Type -> bool

Public Overridable Function IsAssignableFrom (c As Type) As Boolean

Parametreler

c

Type

Geçerli türle Karşılaştırılacak tür.

Döndürülenler

Boolean

true Aşağıdaki koşullardan herhangi biri doğruysa:

• c ve geçerli örnek aynı türü temsil eder.

• c geçerli örnekten doğrudan veya dolaylı olarak türetilir. c geçerli örnekten devralırsa, doğrudan geçerli örnekten türetilir; c Şu anki örnekten devralınan bir veya daha fazla sınıftan devralırsa, geçerli örnekten dolaylı olarak türetilir.

-Geçerli örnek, uygulayan bir arabirimdir c .

• c genel bir tür parametresidir ve geçerli örnek öğesinin kısıtlamalarından birini temsil eder c .

• cbir değer türü temsil eder ve geçerli örnek, null atanabilir < c > 'yi(Visual Basic) temsil eder.

false Bu koşullardan hiçbiri doğru değilse veya ise c null .

Uygulamalar

IsAssignableFrom(Type)

Örnekler

Aşağıdaki örnek, IsAssignableFrom tanımlı sınıflar, tamsayı dizileri ve genel türler kullanılarak yöntemi gösterir.

using namespace System;
using namespace System::Collections::Generic;

ref class Room
{
};

ref class Kitchen : Room
{
};

ref class Bedroom : Room
{
};

ref class Guestroom : Bedroom
{
};

ref class MasterBedroom : Bedroom
{
};

ref class Program
{
public:
    static void Main()
    {
            // Demonstrate classes:
            Console::WriteLine("Defined Classes:");
            Room^ room1 = gcnew Room();
            Kitchen^ kitchen1 = gcnew Kitchen();
            Bedroom^ bedroom1 = gcnew Bedroom();
            Guestroom^ guestroom1 = gcnew Guestroom();
            MasterBedroom^ masterbedroom1 = gcnew MasterBedroom();

            Type^ room1Type = room1->GetType();
            Type^ kitchen1Type = kitchen1->GetType();
            Type^ bedroom1Type = bedroom1->GetType();
            Type^ guestroom1Type = guestroom1->GetType();
            Type^ masterbedroom1Type = masterbedroom1->GetType();

            Console::WriteLine("room assignable from kitchen: {0}", room1Type->IsAssignableFrom(kitchen1Type));
            Console::WriteLine("bedroom assignable from guestroom: {0}", bedroom1Type->IsAssignableFrom(guestroom1Type));
            Console::WriteLine("kitchen assignable from masterbedroom: {0}", kitchen1Type->IsAssignableFrom(masterbedroom1Type));

            // Demonstrate arrays:
            Console::WriteLine();
            Console::WriteLine("Integer arrays:");
            array<Int32>^ array2 = gcnew array<Int32>(2);
            array<Int32>^ array10 = gcnew array<Int32>(10);
            array<Int32, 2>^ array22 = gcnew array<Int32, 2>(2, 2);
            array<Int32, 2>^ array24 = gcnew array<Int32, 2>(2, 4);

            Type^ array2Type = array2->GetType();
            Type^ array10Type = array10->GetType();
            Type^ array22Type = array22->GetType();
            Type^ array24Type = array24->GetType();

            Console::WriteLine("Int32[2] assignable from Int32[10]: {0}", array2Type->IsAssignableFrom(array10Type));
            Console::WriteLine("Int32[2] assignable from Int32[2,4]: {0}", array2Type->IsAssignableFrom(array24Type));
            Console::WriteLine("Int32[2,4] assignable from Int32[2,2]: {0}", array24Type->IsAssignableFrom(array22Type));

            // Demonstrate generics:
            Console::WriteLine();
            Console::WriteLine("Generics:");

            // Note that "int?[]" is the same as "Nullable<int>[]"
            //int?[] arrayNull = new int?[10];
            array<Nullable^>^ arrayNull = gcnew array<Nullable^>(10);
            List<Int32>^ genIntList = gcnew List<Int32>();
            List<Type^>^ genTList = gcnew List<Type^>();

            Type^ arrayNullType = arrayNull->GetType();
            Type^ genIntListType = genIntList->GetType();
            Type^ genTListType = genTList->GetType();

            Console::WriteLine("Int32[10] assignable from Nullable[10]: {0}", array10Type->IsAssignableFrom(arrayNullType));
            Console::WriteLine("List<Int32> assignable from List<Type^>: {0}", genIntListType->IsAssignableFrom(genTListType));
            Console::WriteLine("List<Type^> assignable from List<Int32>: {0}", genTListType->IsAssignableFrom(genIntListType));

            Console::ReadLine();
    }
};

int main()
{
    Program::Main();
}

//This code example produces the following output:
//
// Defned Classes:
// room assignable from kitchen: True
// bedroom assignable from guestroom: True
//kitchen assignable from masterbedroom: False
//
// Integer arrays:
// Int32[2] assignable from Int32[10]: True
// Int32[2] assignable from Int32[2,4]: False
// Int32[2,4] assignable from Int32[2,2]: True
//
// Generics:
// Int32[10] assignable from Nullable[10]: False
// List<Int32> assignable from List<Type^>: False
// List<Type^> assignable from List<Int32>: False

using System;
using System.Collections.Generic;
class Program
{
    public static void Main()
    {
            // Demonstrate classes:
            Console.WriteLine("Defined Classes:");
            Room room1 = new Room();
            Kitchen kitchen1 = new Kitchen();
            Bedroom bedroom1 = new Bedroom();
            Guestroom guestroom1 = new Guestroom();
            MasterBedroom masterbedroom1 = new MasterBedroom();

            Type room1Type = room1.GetType();
            Type kitchen1Type = kitchen1.GetType();
            Type bedroom1Type = bedroom1.GetType();
            Type guestroom1Type = guestroom1.GetType();
            Type masterbedroom1Type = masterbedroom1.GetType();

            Console.WriteLine("room assignable from kitchen: {0}", room1Type.IsAssignableFrom(kitchen1Type));
            Console.WriteLine("bedroom assignable from guestroom: {0}", bedroom1Type.IsAssignableFrom(guestroom1Type));
            Console.WriteLine("kitchen assignable from masterbedroom: {0}", kitchen1Type.IsAssignableFrom(masterbedroom1Type));

            // Demonstrate arrays:
            Console.WriteLine();
            Console.WriteLine("Integer arrays:");

            int[] array2 = new int[2];
            int[] array10 = new int[10];
            int[,] array22 = new int[2, 2];
            int[,] array24 = new int[2, 4];

            Type array2Type = array2.GetType();
            Type array10Type = array10.GetType();
            Type array22Type = array22.GetType();
            Type array24Type = array24.GetType();

            Console.WriteLine("int[2] assignable from int[10]: {0}", array2Type.IsAssignableFrom(array10Type));
            Console.WriteLine("int[2] assignable from int[2,4]: {0}", array2Type.IsAssignableFrom(array24Type));
            Console.WriteLine("int[2,4] assignable from int[2,2]: {0}", array24Type.IsAssignableFrom(array22Type));

            // Demonstrate generics:
            Console.WriteLine();
            Console.WriteLine("Generics:");

            // Note that "int?[]" is the same as "Nullable<int>[]"
            int?[] arrayNull = new int?[10];
            List<int> genIntList = new List<int>();
            List<Type> genTList = new List<Type>();

            Type arrayNullType = arrayNull.GetType();
            Type genIntListType = genIntList.GetType();
            Type genTListType = genTList.GetType();

            Console.WriteLine("int[10] assignable from int?[10]: {0}", array10Type.IsAssignableFrom(arrayNullType));
            Console.WriteLine("List<int> assignable from List<Type>: {0}", genIntListType.IsAssignableFrom(genTListType));
            Console.WriteLine("List<Type> assignable from List<int>: {0}", genTListType.IsAssignableFrom(genIntListType));

            Console.ReadLine();
    }
}
class Room
{
}

class Kitchen : Room
{
}

class Bedroom : Room
{
}

class Guestroom : Bedroom
{
}

class MasterBedroom : Bedroom
{
}

//This code example produces the following output:
//
// Defned Classes:
// room assignable from kitchen: True
// bedroom assignable from guestroom: True
// kitchen assignable from masterbedroom: False
//
// Integer arrays:
// int[2] assignable from int[10]: True
// int[2] assignable from int[2,4]: False
// int[2,4] assignable from int[2,2]: True
//
// Generics:
// int[10] assignable from int?[10]: False
// List<int> assignable from List<Type>: False
// List<Type> assignable from List<int>: False

Imports System.Collections.Generic

Module Example
    Public Sub Main()
        Console.WriteLine("Defined Classes:")
        Dim room1 As New Room()
        Dim kitchen1 As New Kitchen()
        Dim bedroom1 As New Bedroom()
        Dim guestroom1 As New Guestroom()
        Dim masterbedroom1 As New MasterBedroom()

        Dim room1Type As Type = room1.GetType()
        Dim kitchen1Type As Type = kitchen1.GetType()
        Dim bedroom1Type As Type = bedroom1.GetType()
        Dim guestroom1Type As Type = guestroom1.GetType()
        Dim masterbedroom1Type As Type = masterbedroom1.GetType()

        Console.WriteLine("room assignable from kitchen: {0}", room1Type.IsAssignableFrom(kitchen1Type))
        Console.WriteLine("bedroom assignable from guestroom: {0}", bedroom1Type.IsAssignableFrom(guestroom1Type))
        Console.WriteLine("kitchen assignable from masterbedroom: {0}", kitchen1Type.IsAssignableFrom(masterbedroom1Type))

        ' Demonstrate arrays:
        Console.WriteLine()
        Console.WriteLine("Integer arrays:")

        Dim array10(10) As Integer
        Dim array2(2) As Integer
        Dim array22(2, 2) As Integer
        Dim array24(2, 4) As Integer

        Dim array10Type As Type = array10.GetType
        Dim array2Type As Type = array2.GetType
        Dim array22Type As Type = array22.GetType
        Dim array24Type As Type = array24.GetType

        Console.WriteLine("Integer(2) assignable from Integer(10): {0}", array2Type.IsAssignableFrom(array10Type))
        Console.WriteLine("Integer(2) assignable from Integer(2,4): {0}", array2Type.IsAssignableFrom(array24Type))
        Console.WriteLine("Integer(2,4) assignable from Integer(2,2): {0}", array24Type.IsAssignableFrom(array22Type))

        ' Demonstrate generics:
        Console.WriteLine()
        Console.WriteLine("Generics:")

        Dim arrayNull(10) As Nullable(Of Integer)
        Dim genIntList As New List(Of Integer)
        Dim genTList As New List(Of Type)

        Dim arrayNullType As Type = arrayNull.GetType
        Dim genIntListType As Type = genIntList.GetType
        Dim genTListType As Type = genTList.GetType

        Console.WriteLine("Integer(10) assignable from Nullable(Of Integer)(10): {0}", array10Type.IsAssignableFrom(arrayNullType))
        Console.WriteLine("List(Of Integer) assignable from List(Of Type): {0}", genIntListType.IsAssignableFrom(genTListType))
        Console.WriteLine("List(Of Type) assignable from List(Of Integer): {0}", genTListType.IsAssignableFrom(genIntListType))
        Console.ReadLine()
    End Sub
End Module

Class Room
End Class

Class Kitchen : Inherits Room
End Class

Class Bedroom : Inherits Room
End Class

Class Guestroom : Inherits Bedroom
End Class

Class MasterBedroom : Inherits Bedroom
End Class
' The example displays the following output:
'    Defined Classes:
'    room assignable from kitchen: True
'    bedroom assignable from guestroom: True
'    kitchen assignable from masterbedroom: False
'
'    Integer arrays:
'    Integer(2) assignable from Integer(10): True
'    Integer(2) assignable from Integer(2,4): False
'    Integer(2,4) assignable from Integer(2,2): True
'
'    Generics:
'    Integer(10) assignable from Nullable(Of Integer)(10): False
'    List(Of Integer) assignable from List(Of Type): False
'    List(Of Type) assignable from List(Of Integer): False

Aşağıdaki örnekte, geçerli örnek, Type sınıfını temsil eden bir nesnedir Stream . GenericWithConstraint Genel tür parametresi türünde olması gereken genel bir tür Stream . Genel tür parametresini yöntemine geçirmek, IsAssignableFrom genel tür parametresinin bir örneğinin bir nesneye atanamayacağını gösterir Stream .

using System;
using System.IO;

public class Example
{
   public static void Main()
   {
      Type t = typeof(Stream);
      Type genericT = typeof(GenericWithConstraint<>);
      Type genericParam = genericT.GetGenericArguments()[0];
      Console.WriteLine(t.IsAssignableFrom(genericParam));  
      // Displays True.
   }
}

public class GenericWithConstraint<T> where T : Stream
{}

Imports System.IO

Module Example
   Public Sub Main()
      Dim t As Type = GetType(Stream)
      Dim genericT As Type = GetType(GenericWithConstraint(Of ))
      Dim genericParam As Type = genericT.GetGenericArguments()(0)
      Console.WriteLine(t.IsAssignableFrom(genericParam))  
      ' Displays True.
   End Sub
End Module

Public Class GenericWithConstraint(Of T As Stream)
End Class

Açıklamalar

IsAssignableFromYöntemi, bir örneğinin c geçerli türdeki bir örneğe atanıp atanamayacağını tespit etmek için kullanılabilir, ve aşağıdaki örnekte gösterildiği gibi, türleri tasarım zamanında bilinmeyen ve koşullu atamaya izin veren nesneleri işlerken Yöntem en yararlı seçenektir.

using System;
using System.Collections;

public class Example
{
   public static void Main()
   {
      Type t = typeof(IEnumerable);
      Type c = typeof(Array);
      
      IEnumerable instanceOfT;
      int[] instanceOfC = { 1, 2, 3, 4 };
      if (t.IsAssignableFrom(c))
         instanceOfT = instanceOfC;
  }
}

Imports System.Collections

Module Example
   Public Sub Main()
      Dim t As Type = GetType(IEnumerable)
      Dim c As Type = GetType(Array)
      
      Dim instanceOfT As IEnumerable
      Dim instanceOfC As Integer() = { 1, 2, 3, 4 }
      If t.IsAssignableFrom(c) Then
         instanceOfT = instanceOfC
      End If  
   End Sub
End Module

Bu nedenle, aşağıdaki gibi bir kod satırının InvalidCastException özel durum veya benzer bir özel durum oluşturmadan çalışma zamanında yürütülmesi gerekir:

instanceOfT = instanceOfC;

instanceOfT = instanceOfC

Bu yöntem türetilmiş bir sınıf tarafından geçersiz kılınabilir.

Not

Genel tür tanımı kapalı oluşturulmuş bir türden atanamaz. diğer bir deyişle, kapalı oluşturulmuş türü MyGenericList<int> ( MyGenericList(Of Integer) Visual Basic) türünden bir değişkene atayamazsınız MyGenericList<T> .

cParametresi tür ise TypeBuilder , sonuç oluşturulacak türe göre belirlenir. Aşağıdaki kod örneği, adlı derlenmiş bir tür kullanarak bunu gösterir B .

using System;
using System.Reflection;
using System.Reflection.Emit;

public class A
{}

public class Example
{
   public static void Main()
   {
      AppDomain domain = AppDomain.CurrentDomain;
      AssemblyName assemName = new AssemblyName();
      assemName.Name = "TempAssembly";

      // Define a dynamic assembly in the current application domain.
      AssemblyBuilder assemBuilder = domain.DefineDynamicAssembly(assemName,
                                            AssemblyBuilderAccess.Run);

      // Define a dynamic module in this assembly.
      ModuleBuilder moduleBuilder = assemBuilder.DefineDynamicModule("TempModule");

      TypeBuilder b1 = moduleBuilder.DefineType("B", TypeAttributes.Public, typeof(A));
      Console.WriteLine(typeof(A).IsAssignableFrom(b1));
   }
}
// The example displays the following output:
//        True

Imports System.Reflection
Imports System.Reflection.Emit

Public Class A
End Class

Module Example
   Public Sub Main()
      Dim domain As AppDomain = AppDomain.CurrentDomain
      Dim assemName As New AssemblyName()
      assemName.Name = "TempAssembly"

      ' Define a dynamic assembly in the current application domain.
      Dim assemBuilder As AssemblyBuilder = domain.DefineDynamicAssembly(assemName,
                                                   AssemblyBuilderAccess.Run)

      ' Define a dynamic module in this assembly.
      Dim moduleBuilder As ModuleBuilder = assemBuilder.DefineDynamicModule("TempModule")

      Dim b1 As TypeBuilder = moduleBuilder.DefineType("B", TypeAttributes.Public, GetType(A))
      Console.WriteLine(GetType(A).IsAssignableFrom(b1))
   End Sub
End Module
' The example displays the following output:
'       True