A sealed class cannot be inherited. It is an error to use a sealed class as a base class. Use the sealed modifier in a class declaration to prevent inheritance of the class.

It is not permitted to use the abstract modifier with a sealed class.

Structs are implicitly sealed; therefore, they cannot be inherited.

Example

// cs_sealed_keyword.cs
// Sealed classes
using System;
sealed class MyClass 
{
   public int x; 
   public int y;
}

class MainClass 
{
   public static void Main() 
   {
      MyClass mC = new MyClass(); 
      mC.x = 110;
      mC.y = 150;
      Console.WriteLine("x = {0}, y = {1}", mC.x, mC.y); 
   }
}

Output

x = 110, y = 150

In the preceding example, if you attempt to inherit from the sealed class by using a statement like this:

class MyDerivedC: MyClass {}   // Error

you will get the error message:

'MyDerivedC' cannot inherit from sealed class 'MyBaseC'.

See Also

C# Keywords | Modifiers