What’s the best strategy for Equals and GetHashCode?

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Domain-Driven Design makes the distinction between Entities and Value Objects. This is a good distinction to observe since it guides how you implement Equals.

Entities are equal if their IDs equal each other.

Value Objects are equal if all their (important) constituent elements are equal to each other.

In any case, the implementation of GetHashCode should base itself on the same values that are used to determine equality. In other words, for Entities, the hash code should be calculated directly from the ID, whereas for Value Objects it should be calculated from all the constituent values.

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