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How to prevent class from overriding?

Posted By :Maverick     Posted Date :July 31, 2011    Points :40   Category :.NET Framework 
We can define the class as sealed in C#.net and "Norinheritable" in VB.NET.

You can also find related Interview Question to How to prevent class from overriding?  below: 

Can you allow class to be inherited, but prevent the method from being over-ridden?

Yes, just leave the class public and make the method sealed. (More...)

Can you prevent a class from Inheriting?

Yes, by defining the class as 'Sealed' (More...)

What is the difference between a Struct and a Class?

The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is less expensive.

When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will remain unassigned and the object cannot be used until all of the fields are initialized.

It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always provided to initialize the struct members to their default values.

It is an error to initialize an instance field in a struct.

There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.

A struct is a value type, while a class is a reference type. (More...)

What is Method Overriding? How to override a function in C#?

Use the override modifier to modify a method, a property, an indexer, or an event. An override method provides a new implementation of a member inherited from a base class. The method overridden by an override declaration is known as the overridden base method. The overridden base method must have the same signature as the override method.
You cannot override a non-virtual or static method. The overridden base method must be virtual, abstract, or override. (More...)

Can we call a base class method without creating instance?

Its possible If its a static method.

Its possible by inheriting from that class also.

Its possible from derived classes using base keyword. (More...)

What is Private Constructor? and it's use? Can you create instance of a class which has Private Constructor?

When a class declares only private instance constructors, it is not possible for classes outside the program to derive from the class or to directly create instances of it. (Except Nested classes)
Make a constructor private if:

1) You want it to be available only to the class itself. For example, you might have a special constructor used only in the implementation of your class' Clone method.

2) You do not want instances of your component to be created. For example, you may have a class containing nothing but Shared utility functions, and no instance data. Creating instances of the class would waste memory. (More...)

What is the difference between interface and abstract class ?

a class may inherit several interfaces, a class may inherit only one abstract class (More...)

Differentiate between a template class and class template.

Template class:
A generic definition or a parameterized class not instantiated until the client provides the needed information. It's jargon for plain templates.

Class template:
A class template specifies how individual classes can be constructed much like the way a class specifies how individual objects can be constructed. It's jargon for plain classes. (More...)

What is an adaptor class or Wrapper class?

A class that has no functionality of its own. Its member functions hide the use of a third party software component or an object with the non-compatible interface or a non- object- oriented implementation. (More...)

What is class invariant?

A class invariant is a condition that defines all valid states for an object. It is a logical condition to ensure the correct working of a class. Class invariants must hold when an object is created, and they must be preserved under all operations of the class. In particular all class invariants are both preconditions and post-conditions for all operations or member functions of the class. (More...)

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