C# Language
C# Equality and Hash Collections
Custom IEqualityComparer<T>: One Policy Across Distinct, GroupBy, Join and Dictionaries

Lesson6 / 12

Module 1 · Equality, comparers and reliable keys1 locked3 lessons

Module 2 · Records, Structs and Custom Comparers4 locked4 lessons

04Record Equality in Practice: Collection Members, Inheritance and Mutable Keys (included with Full Access)
05Struct Equality: Boxing, One-Field Hash Codes and Floating-Point Keys (included with Full Access)
06Custom IEqualityComparer<T>: One Policy Across Distinct, GroupBy, Join and Dictionaries (included with Full Access)
07Hash Quality: Counting Collisions, HashCode.Combine and Per-Process String Hashes (included with Full Access)

Module 3 · Ordering, Collections and Identity4 locked4 lessons

08Ordering Is Not Equality: Comparers, Sorted Collections and Culture-Aware Strings (included with Full Access)
09Collections as Values: Structural Equality, Set Keys and Frozen Lookups (included with Full Access)
10Dictionary APIs That Decide Correctness: TryAdd, In-Place Updates, GetOrAdd and Span Lookups (included with Full Access)
11Entity Identity: Id-Based Equals, Transient Objects and Hash Codes That Change (included with Full Access)

Module 4 · Practice and Assessment1 locked1 lesson

12Final Mock Interview: 25 Questions on C# Equality and Hash Collections (included with Full Access)

Module 2 · Records, Structs and Custom Comparers · Lesson 6 of 12

Custom IEqualityComparer<T>: One Policy Across Distinct, GroupBy, Join and Dictionaries

13 min readTechInterviewNotes Editorial TeamUpdated 27 Oct 2026Save

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TechInterviewNotes Editorial Team · Updated 27 Oct 2026 ·