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Editorial Team
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Asked: 2026-05-16T15:03:25+00:00

Basically, Nullable<T> is a structure, which explains things like calling .HasValue will never throw

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Basically, Nullable<T> is a structure, which explains things like calling .HasValue will never throw a NullReferenceException. I was wondering why – given a nullable which does not have a value – comparisons to null are always true, even when using Object.ReferenceEquals, which I thought would return false because it is a structure.

Is there special behaviour built into the CLR to make this possible? It would probably also explain why the generic struct constraint does not allow nullables.

Best Regards,
Oliver Hanappi

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1 Answer

  1. Editorial Team

    If you do:

    int? x = null;
if (x == null)

    that will use HasValue.

    Using Object.ReferenceEquals will box the value first – and that will convert the null value into a null reference (which is indeed special CLR behaviour). When a nullable value type is boxed, the result is either a null reference or a box of the underlying value type. In other words, there’s no such thing as a boxed value of a nullable value type.

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