How sealed Class Improve performance

Question

Can any one tell me how sealed class improve performance in C sharp?

Vulpes · Answer

If the CLR sees that a class is sealed then it knows that it cannot be inherited from which enables it to make certain optimizations. For example if a virtual method of a sealed class is called then this can be converted to a non-virtual call (which is quicker) because there's no chance that it can be called by an object of a derived class.

Vulpes · Answer

Incidentally unless you're writing a performance critical application I wouldn't worry about making your classes sealed. If the C# language designers had thought this important they'd probably have made classes sealed by default. If you're writing a library for others to use then a more important consideration is whether it's a good idea to allow them to inherit from your classes - sometimes it isn't and you'll therefore find that some classes in the .NET framework itself are sealed. As well as making a whole class sealed you can also seal an 'override' method in isolation to prevent further overriding. Again this would usually be done for design rather than performance reasons.

Rahul Shah · Answer

Yeah...I got it now..

Vulpes · Answer

It's still virtual because if Derived were not sealed then MyMethod() could be overridden again by another class which derives from Derived.

Rahul Shah · Answer

But I am not getting that how override method in derive class is Still Virtual

Vulpes · Answer

You're right that a sealed class can't contain new virtual methods but it can contain overrides of virtual methods which are still virtual. For example the following compiles fine: class Parent { public virtual void MyMethod(){} } sealed class Derived : Parent { public override void MyMethod() {} }

Rahul Shah · Answer

But sealed class does not contains Virtual methods. It will gives an error if we declare virtual method in sealed class.