Is And As Operators Explained With An UML

Both of these two operators -- is and as - execute at run time.

The is operator

The is operator is used for checking whether the object is compatible or not.

It returns true if the given object is of the same type, else it returns false.
It also returns false if the object is null.
Syntax - The following code checks if object is a SmartPhone or not.
1. if(obj is SmartPhone)

This operator is used for conversion between compatible reference types.
It returns the object if they are compatible, else it returns null.
Syntax - The following code coverts obj into SmartPhone. It's called typecasting.
1. SmartPhone smartPhone = obj as SmartPhone;

Let's create a basic UML, then we will implement classes as per the UML, to understand these 2 operators.

Base class - Phone
Base Interface - ISmartPhone
Derived class - SmartPhone implementing an interface ISmartPhone & extending a class Phone

As per this implementation, we know that every SmartPhone is a Phone as well as ISmartPhone
But not every phone is a SmartPhone. As in the real world, some phones are just meant for calling & texting.

Let's start coding.

First, Base classes and interfaces:

Now the real deal, SmartPhone class,

Lastly, we need to call this structure through the Main method,

VerifyTheSmartPhone(): It takes an object as a parameter & checks if that object is a SmartPhone or not
If it is a SmartPhone then it calls the DisplayObject method of that SmartPhone
Else it will display a message
These operators help to handle the exception at runtime
Calling of VerifyTheSmartPhone(obj)

First, pass SmartPhone object
Second, pass Phone's object (Remember as per our UML, not all the Phones are SmartPhones)
Third, Another SmartPhone object.
1. class Program
2. {
3. static void Main(string[] args)
4. {
5. object obj = new SmartPhone() { Name = "IPhone X", Price = 110000 };
6. VerifyTheSmartPhone(obj);
8. Phone notASmartPhone = new Phone();
9. VerifyTheSmartPhone(notASmartPhone);
11. ISmartPhone interfaceReference = new SmartPhone() { Name = "One Plus 8", Price = 65000 };
12. VerifyTheSmartPhone(interfaceReference);
13. }
15. /// <summary>
16. /// This methods checks if parameter is an smart phone type
17. /// </summary>
18. /// <param name="obj"></param>
19. /// <returns>true if parameter is a smart phone</returns>
20. static bool VerifyTheSmartPhone(object obj)
21. {
22. if(obj is SmartPhone)
23. {
24. SmartPhone smartPhone = (SmartPhone)obj;
25. System.Console.WriteLine(smartPhone.DisplayObject());
26. return true;
27. }
28. else
29. {
30. System.Console.WriteLine("It is not a SmartPhone object");
31. return false;
32. }
33. }
34. }

Let's see if this works.

Hooray!! Both operators worked as expected.

In this article, we learned:

Thank you all, I hope you enjoyed the knowledge shared in this article.