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Aporeon interview preparation

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C# OOP & Type Design Essentials

Objects, encapsulation, abstraction, interfaces, inheritance, composition, polymorphism, access boundaries, construction, immutability, equality, and collaboration.

15 drillsPractice one at a timeOrdered pathConcept questionDebugging scenarioComparison questionArchitecture scenario

Recommended start

Model useful objects

Starts object-oriented design from cohesive state and behavior instead of creating classes for every noun in a requirement.

Easy~5 minStep 1 of 15

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1Model useful objectsRecommended startStarts object-oriented design from cohesive state and behavior instead of creating classes for every noun in a requirement.Concept questionEasy~5 min.NETC#Practice 2EncapsulationUses controlled state transitions and intention-revealing APIs to keep objects valid rather than treating encapsulation as private fields alone.Concept questionEasy~5 min.NETC#Practice 3Abstraction vs encapsulationSeparates hiding implementation complexity from controlling access to state, with practical examples where both ideas work together.Concept questionEasy~5 min.NETC#Practice 4Interface vs abstract classChooses contracts and shared implementation based on substitutability, state ownership, evolution, and inheritance constraints.Concept questionMedium~7 min.NETC#Practice 5Use inheritance safelyUses inheritance only for stable behavioral subtyping and tests whether derived objects preserve the promises callers rely on.Concept questionMedium~7 min.NETC#Practice 6Composition over inheritanceCombines focused collaborators for independent behavior while recognizing cases where a genuine stable hierarchy remains simpler.Concept questionMedium~7 min.NETC#Practice 7Runtime polymorphismExplains how callers use one contract while runtime dispatch selects implementation, then connects that mechanism to extensible behavior.Concept questionMedium~7 min.NETC#Practice 8Method dispatch in C#Separates compile-time overload selection from runtime virtual dispatch and diagnoses method hiding through a base reference.Debugging scenarioHard~12 min.NETC#Practice 9Access modifiersUses public, internal, protected, private, and protected internal deliberately to control API surface and inheritance exposure.Concept questionEasy~5 min.NETC#Practice 10Object constructionCreates valid objects with clear intent while choosing construction patterns proportionally to optional data, validation, and lifecycle complexity.Concept questionMedium~7 min.NETC#Practice 11ImmutabilityChooses immutable values and controlled mutable entities based on identity, concurrency, invariants, allocation cost, and update semantics.Concept questionMedium~7 min.NETC#Practice 12Static vs instance stateUses static members for type-wide stateless behavior and constants while avoiding hidden global mutable state and lifetime problems.Concept questionEasy~5 min.NETC#Practice 13Records, classes, and structsChooses a type shape from identity, value semantics, mutation, copy cost, default values, and serialization boundaries.Comparison questionMedium~7 min.NETC#Practice 14Equality and hash codesConnects equality semantics to hash-based collections and chooses identity or value equality deliberately.Concept questionMedium~7 min.NETC#Practice 15Object collaborationMoves invariant-sensitive decisions toward the owning object while keeping orchestration, queries, and cross-boundary work appropriately explicit.Architecture scenarioHard~12 min.NETC#Practice

Practice order

15 drillsOne at a time

1Model useful objectsUp next / Easy / ~5 min
2EncapsulationEasy / ~5 min
3Abstraction vs encapsulationEasy / ~5 min
4Interface vs abstract classMedium / ~7 min
5Use inheritance safelyMedium / ~7 min
6Composition over inheritanceMedium / ~7 min
7Runtime polymorphismMedium / ~7 min
8Method dispatch in C#Hard / ~12 min

+7 more drills in this section