Abstract classes in C#
C# interview exercise on Classes & Records, difficulty 2 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Make Shape abstract, with an abstract Area() and a concrete Describe() that returns "<TypeName> with area <area to 1 decimal>". Then finish Square and Circle (using Math.PI).
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.