This can be useful in situations where we need the specific functionality of the derived class.Īnother advantage of downcasting is that it can make code more flexible and extensible. The primary advantage of downcasting is that it allows access to the derived class’s specific methods and properties that are not available in the base class. Thus, we can see how downcasting is useful in event handling to access the specific functionality of a derived class even though an object of the base class raised the event. If the downcasting is successful (i.e., owl is indeed of type Owl), we call the Fly() method of the Owl class. Here, we are using pattern matching to simplify the process of checking the type and assigning it to a variable in a single operation. Then, we downcast the Animal property of the AnimalEventArgs object to an Owl object and assign it to a variable owl. Here, we create an event handler animalEventHandler that takes two parameters, the sender object, i.e., the object that raised the event, and an instance of AnimalEventArgs. Here, DerivedClass is the name of the derived class, and baseObject is the base class reference that needs to be downcasted.ĮventHandler animalEventHandler = (sender, args) => In C#, downcasting works by explicitly converting a base class reference to a derived class reference using the cast operator:ĭerivedClass derivedObject = (DerivedClass) baseObject Downcasting in C#ĭowncasting is a technique that allows us to treat a base class object as an instance of its derived class. The code throws a compiler error “ ‘Animal’ does not contain a definition for ‘Move’ and no accessible extension method ‘Move’ accepting a first argument of type ‘Animal’ could be found (are you missing a using directive or an assembly reference?)“. Here, once we upcast Snake to Animal, we lose access to the Move() method defined in the Snake class. So, if the derived class contains a method or a property that the base class does not, we cannot access it through the base class reference: Animal animal = new Snake() One of the major limitations of upcasting is that it does not allow access to the derived class’s unique methods or properties. NET/C# content and get paid? > JOIN US! << Limitations of Upcasting Wanna join Code Maze Team, help us produce more awesome. Additionally, storing objects of different derived classes in a single collection can help us manage the code more efficiently and avoid creating separate collections for each derived class. Upcasting can also help us avoid duplicating code for different derived classes and make the code more concise. This can help us uniformly treat different types of objects, as we can use the base class to represent several derived classes. Upcasting simplifies the code and makes it more flexible.īy upcasting objects to a common base class, we can add them to a collection and call methods on them that are defined in the base class without worrying about their specific types. In this scenario, we can upcast and store all the objects in the collection using the base class reference. With upcasting, we can pass the derived class object as a base class object, and the function can perform the necessary operations on it.Īnother use case is when a collection of objects of different derived classes needs to be stored in a single collection. Thus, we can see how upcasting can be useful when we want to treat different types of objects uniformly.Ī common use of upcasting is when we need to pass a derived class object to a function that only accepts the base class object. This is because both Snake and Owl implement the MakeSound() method, which is defined in the base Animal class: foreach (var animalObj in animals)Ĭonsole.WriteLine("It says: " + animalObj.MakeSound()) Then, we can iterate over the list of Animal objects and call the MakeSound() method on each one, without worrying about their specific types.
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