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BillWagner merged 3 commits into from
Jun 30, 2026
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Document sizeof behavior on enum types #54560

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af34dd7
Document sizeof behavior on enum types
heissenberg06 Jun 28, 2026
496bdcf
Clarify that sizeof on enum types doesn't require unsafe context
heissenberg06 Jun 29, 2026
ec3c1df
Update docs/csharp/language-reference/operators/sizeof.md
BillWagner Jun 30, 2026
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5 changes: 3 additions & 2 deletions docs/csharp/language-reference/operators/sizeof.md
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@@ -1,7 +1,7 @@
---
title: "sizeof operator - determine the storage needs for a type"
description: "Learn about the C# `sizeof` operator that returns the memory amount occupied by a variable of a given type."
ms.date: 06/16/2026
ms.date: 06/29/2026
f1_keywords:
- "sizeof_CSharpKeyword"
- "sizeof"
Expand All @@ -10,7 +10,7 @@ helpviewer_keywords:
---
# sizeof operator - determine the memory needs for a given type

The `sizeof` operator returns the number of bytes occupied by a variable of a given type. In safe code, the argument to the `sizeof` operator must be the name of a built-in [unmanaged type](../builtin-types/unmanaged-types.md) whose size isn't platform-dependent.
The `sizeof` operator returns the number of bytes occupied by a variable of a given type. In safe code, the argument to the `sizeof` operator must be the name of a built-in [unmanaged type](../builtin-types/unmanaged-types.md) whose size isn't platform-dependent, or an [enumeration type](../builtin-types/enum.md).

[!INCLUDE[csharp-version-note](../includes/initial-version.md)]

Expand Down Expand Up @@ -41,6 +41,7 @@ In [unsafe](../keywords/unsafe.md) code, you can use `sizeof` on any non-`void`

- The size of a reference or pointer type is the size of a reference or pointer, not the size of the object it might refer to.
- The size of a value type, unmanaged or not, is the size of such a value.
- The size of an enumeration type is the size of its underlying integral type. This size is a compile-time constant. If the underlying type of an enum defined in a referenced assembly later changes, code that applied `sizeof` to that enum must be recompiled to observe the new size.
- The size of a `ref struct` type is the size of the value. The size of every `ref` field is the size of a reference or pointer, not the size of the value it refers to.

The following example demonstrates the usage of the `sizeof` operator:
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