| title | description | ms.date | ms.topic | f1_keywords | helpviewer_keywords | author | ms.author | manager | ms.subservice | dev_langs | monikerRange | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
CA1403: Auto layout types should not be COM visible |
A COM-visible value type is marked with the System.Runtime.InteropServices.StructLayoutAttribute attribute set to LayoutKind.Auto. |
11/04/2016 |
reference |
|
|
mikejo5000 |
mikejo |
mijacobs |
code-analysis |
|
vs-2019 |
| Item | Value |
|---|---|
| RuleId | CA1403 |
| Category | Microsoft.Interoperability |
| Breaking change | Breaking |
A Component Object Model (COM) visible value type is marked with the xref:System.Runtime.InteropServices.StructLayoutAttribute?displayProperty=fullName attribute set to xref:System.Runtime.InteropServices.LayoutKind.Auto?displayProperty=fullName.
xref:System.Runtime.InteropServices.LayoutKind layout types are managed by the common language runtime. The layout of these types can change between versions of .NET, which breaks COM clients that expect a specific layout. If the xref:System.Runtime.InteropServices.StructLayoutAttribute attribute is not specified, the C#, Visual Basic, and C++ compilers specify LayoutKind.Auto for value types.
Unless marked otherwise, all public, non-generic types are visible to COM, and all non-public and generic types are invisible to COM. However, to reduce false positives, this rule requires the COM visibility of the type to be explicitly stated. The containing assembly must be marked with the xref:System.Runtime.InteropServices.ComVisibleAttribute?displayProperty=fullName set to false and the type must be marked with the xref:System.Runtime.InteropServices.ComVisibleAttribute set to true.
To fix a violation of this rule, change the value of the xref:System.Runtime.InteropServices.StructLayoutAttribute attribute to LayoutKind.Explicit or LayoutKind.Sequential, or make the type invisible to COM.
Do not suppress a warning from this rule.
The following example shows a type that violates the rule and a type that satisfies the rule.
:::code language="csharp" source="../snippets/csharp/VS_Snippets_CodeAnalysis/FxCop.Interoperability.AutoLayout/cs/FxCop.Interoperability.AutoLayout.cs" id="Snippet1":::