C# Equals, GetHashCode, and Hash Collection Semantics

If an object is used in Dictionary or HashSet, overriding only Equals is not enough. GetHashCode must match the equality semantics.

Hash collections usually locate a bucket by hash code first, then confirm equality. If two logically equal objects produce different hash codes, lookup, removal, or de-duplication may fail.

Best Practices

• Implement Equals and GetHashCode together when defining value equality.
• Prefer immutable objects as hash keys.
• Do not generate hash codes from random or mutable state.
• Consider records when they fit value-object semantics.