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What is downcasting and upcasting? (.NET interview questions with answers) has created an awesome video for this question which is available at this link

“Upcasting” means moving subclass object to the parent class object. “DownCasting” is opposite to “Upcasting” moving the parent object to the child object.


“Upcasting” is perfectly valid but “Downcasting” is not allowed in .NET. For instance below is a simple “Customer” parent class which is further inherited by a child class “GoldCustomer”.

class Customer


class GoldCustomer : Customer



Below is an “upcasting” code where the child parent class gold customer is pushed to the customer class.

Customer obj = new GoldCustomer();

Below is a sample of “downcasting” code where parent class object is tried to move to a child class object, this is not allowed in .NET.

GoldCustomer obj = new Customer(); // not allowed illegal

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