Sealed Classes

Sealed Classes

A sealed class cannot be inherited from at all, preventing any further subclassing. You can also seal an individual override method so deeper subclasses can't override it again. Sealing is often used for security, performance, or to lock down a design that shouldn't be extended.

Note: Sealing a class can let the compiler apply certain optimizations since the type hierarchy is known to stop there.

Example: Sealed Classes

using System;

sealed class FinalConfig
{
    public string Version = "1.0";

    public void Show()
    {
        Console.WriteLine($"Config version {Version}");
    }
}

class Program
{
    static void Main(string[] args)
    {
        FinalConfig config = new FinalConfig();
        config.Show();
        // class Extended : FinalConfig {} would be a compile error
    }
}