CategoryInheritance

Explicit Interface member implementations

Explicit Interface are implemented explicitly if for example two or more of our interfaces implement same method/properties/etc… names and different implementation. Other usages can be to implement strong typing and cleaner code.

 

 

Implicit Interface member implementations

Example will show how to create new interface called ICarSpecifications which will hold a property and a method. ICarSpecifications interface will be implemented inside Car class and its implementation will be inside region InterfaceImplementation(note: you can manually create implementation OR when you type ICarSpecifications pres keys CTRL + . and click Implement missing members. Region will not be implemented automatically).

 

Tomorrow we will continue with explicit interfaces implementations.

Interfaces

Interfaces are a type of contract between interface and class or struct. Interface is defined by interface keyword and the name of interface should usually start with capital letter I to make it more recognizable.

 

When we say Interface is a contract, what do you really mean?

Every class or struct that uses some interface must implement all of its functionalities.
Why would you use Interface at all?

There are multiple reasons actually:

Firstly, a class or classes that use Interface must use all of Interfaces functionalities. Secondly, names of all properties, methods… must be same in all classes as they are in that specific Interface. Furthermore Interfaces are obligatory, imagine situation where you must in a few classes use 3 methods Get, Insert and Delete, when you use interface with your classes there is no possibility of forgetting to implement either of these methods. Lastly, because C# does not allow us to inherit multiple classes but allows us to implement multiple Interfaces, we can create multiple interfaces where each interface inherits a class and use these interface as workaround.

 

What can we define inside Interface?

Events

Indexers

Methods (but without implementation)

Properties

 

What are Interface limitations?

Interfaces cannot define:

Constants

Constructors

Fields

Operators

We cannot make interface or its members static

 

What about access modifiers?

By default all interface members are public and we cannot change it.

 

Can we instantiate Interface? Yes we can, limitation is that you must instantiate them using a class or struct that implements that interface.

 

Is there a limit to how many Interfaces can we implement at the same time? Yes and no. Although language specification state that you can implement as many Interfaces as you like, there are few technical limitations: heap size and metadata tables size, but worry not, you will never exceed that limit.

 

Please, drop by tomorrow to see a few Interface examples .

Explicit Interface member implementations

Implicit Interface member implementations

 

 

 

 

 

Inheritance

Inheritance

What exactly is Inheritance? MSDN explanation says : Inheritance enables you to create new classes that reuse, extend, and modify the behavior that is defined in other classes. The class whose members are inherited is called the base class, and the class that inherits those members is called the derived class. A derived class can have only one direct base class. However, inheritance is transitive. If ClassC is derived from ClassB, and ClassB is derived from ClassA, ClassC inherits the members declared in ClassB and ClassA.

So what can we inherit? For example we have Car and Motorcycle classes, and as we know cars and motorcycles have a few things in common such as engine and color. We could create a base class named Vehicle that has those properties and make Car and Motorcycle classes which will inherit Vehicle class.

 

Can i inherit from multiple classes? No, but you can Inherit multiple Interfaces that inherit one class.

 

I don’t wish for my class or method to be directly instantiated. What can I do about that problem? You can make those classes or methods abstract. Beware, when you make your class abstract one, none of your class members have to be marked as abstract, but if at least one of your members is marked as abstract, entire class must be marked as abstract.

 

Can derived class access private fields of base class? No, it can not. You can only access internal, public, protected, and protected internal members of a base class.

 

Is it possible to prevent our class from becoming other classes base class? Yes, mark that class as sealed and other classes cannot inherit from this class.

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