Determines whether an instance of the current Type can be assigned from an instance of the specified Type.
Assembly: mscorlib (in mscorlib.dll)
Public Overridable Function IsAssignableFrom ( _
c As Type _
) As Booleanpublic virtual bool IsAssignableFrom(
Type c
)public:
virtual bool IsAssignableFrom(
Type^ c
)abstract IsAssignableFrom :
c:Type -> bool
override IsAssignableFrom :
c:Type -> bool Parameters
- c
- Type: System
. . :: . Type
The type to compare with the current type.
Return Value
Type: Systemtrue if c and the current Type represent the same type, or if the current Type is in the inheritance hierarchy of c, or if the current Type is an interface that c implements, or if c is a generic type parameter and the current Type represents one of the constraints of c. false if none of these conditions are true, or if c is
Implements
_TypeThis method can be overridden by a derived class.
Note |
|---|
A generic type definition is not assignable from a closed constructed type. That is, you cannot assign the closed constructed type MyGenericList<int> (MyGenericList(Of Integer) in Visual Basic) to a variable of type MyGenericList<T>. |
You can determine the element types of a Type using GetElementType.
If the c parameter is of type TypeBuilder, the result is based on the type that is to be built. The following code example demonstrates this using a built type named B.
TypeBuilder b1 = moduleBuilder.DefineType("B", TypeAttributes.Public, typeof(A));
// Returns true:
typeof(A).IsAssignableFrom(b1))The following example demonstrates the IsAssignableFrom method using defined classes, integer arrays, and generics.
Imports System
Imports System.Collections.Generic
Class ArrayTypeTest
Public Shared Sub Main()
' Demonstrate classes:
Console.WriteLine("Defned Classes:")
Dim room1 As Room = New Room
Dim kitchen1 As Kitchen = New Kitchen
Dim bedroom1 As Bedroom = New Bedroom
Dim guestroom1 As Guestroom = New Guestroom
Dim masterbedroom1 As MasterBedroom = 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 Class
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
'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:
' 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
using System;
using System.Collections.Generic;
class Program
{
public static void Main()
{
// Demonstrate classes:
Console.WriteLine("Defned 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
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("Defned 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
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Note