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Why does boxing an empty nullable value produce null rather than Nullable<T>?

KitForma editorial guide. Boxing a nullable value follows its presence: no value boxes to null, while a present value boxes as the underlying value type. Reflection code expecting a boxed Nullable<T> can therefore make the wrong type assumption.

csharp nullable-boxing

C# & .NET →

Step-by-step guidance

Boxing a nullable value follows its presence: no value boxes to null, while a present value boxes as the underlying value type. Reflection code expecting a boxed Nullable<T> can therefore make the wrong type assumption. Check for null before inspecting the runtime type, and use the declared type separately when you need nullable schema information. Keep absence distinct from the underlying type’s default value. A minimal C# example is:

csharp

using System;
int? missing = null;
int? present = 7;
object? a = missing;
object? b = present;
Console.WriteLine(a is null);
Console.WriteLine(b?.GetType() == typeof(int));

Both lines should print True. This behavior does not automatically define JSON or database null-handling policy.

Sources and verification

Microsoft .NET documentation: nullablecs

Sources checked: 2 October 2026

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Why does boxing an empty nullable value produce null rather than Nullable<T>?

Step-by-step guidance

Sources and verification

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