Type.IsAbstract Property

Definition

Namespace:

System

Assemblies:

netstandard.dll, System.Runtime.dll

Source:

Type.cs

Gets a value indicating whether the Type is abstract and must be overridden.

C#

public bool IsAbstract { get; }

Property Value

Boolean

true if the Type is abstract; otherwise, false.

Examples

The following example creates an array of Type objects that represent the following types:contains type returns true if the specified object is abstract; otherwise, it returns false.

• AbstractClass, an abstract class (a class marked as abstract in C# and MustInherit in Visual Basic).

• DerivedClass, a class that inherits from AbstractClass.

• SingleClass, a non-inheritable class. it's defined as sealed in C# and NotInheritable in Visual Basic.

• ITypeInfo, an interface.

• ImplementingClass, a class that implements the ITypeInfo interface.

The method returns true only for AbstractClass, the abstract class, and ITypeInfo, the interface.

C#

using System;

public abstract class AbstractClass
{}

public class DerivedClass : AbstractClass
{}

public sealed class SingleClass
{}

public interface ITypeInfo
{
   string GetName();
}

public class ImplementingClass : ITypeInfo
{
   public string GetName()
   {
      return this.GetType().FullName;
   }
}

delegate string InputOutput(string inp);

public class Example
{
   public static void Main()
   {
      Type[] types= { typeof(AbstractClass),
                      typeof(DerivedClass),
                      typeof(ITypeInfo),
                      typeof(SingleClass),
                      typeof(ImplementingClass),
                      typeof(InputOutput) };
      foreach (var type in types)
         Console.WriteLine("{0} is abstract: {1}",
                           type.Name, type.IsAbstract);
   }
}
// The example displays the following output:
//       AbstractClass is abstract: True
//       DerivedClass is abstract: False
//       ITypeInfo is abstract: True
//       SingleClass is abstract: False
//       ImplementingClass is abstract: False
//       InputOutput is abstract: False

Remarks

The IsAbstract property returns true in the following cases:

• The current type is abstract; that is, it cannot be instantiated, but can only serve as the base class for derived classes. In C#, abstract classes are marked with the abstract keyword; in F#, they are marked with the AbstractClass attribute; in Visual Basic, they are marked with the MustInherit keyword.

• The current type is an interface.

If the current Type represents a type parameter in the definition of a generic type or generic method, this property always returns false.

Applies to

See also

• TypeAttributes