CA1408: Do not use AutoDual ClassInterfaceType
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The latest version of this topic can be found at CA1408: Do not use AutoDual ClassInterfaceType.
TypeName|DoNotUseAutoDualClassInterfaceType|
|CheckId|CA1408|
|Category|Microsoft.Interoperability|
|Breaking Change|Breaking|
A Component Object Model (COM) visible type is marked with the ClassInterfaceAttribute attribute set to the AutoDual value of ClassInterfaceType.
Types that use a dual interface enable clients to bind to a specific interface layout. Any changes in a future version to the layout of the type or any base types will break COM clients that bind to the interface. By default, if the ClassInterfaceAttribute attribute is not specified, a dispatch-only interface is used.
Unless marked otherwise, all public nongeneric types are visible to COM; all nonpublic and generic types are invisible to COM.
To fix a violation of this rule, change the value of the ClassInterfaceAttribute attribute to the None value of ClassInterfaceType and explicitly define the interface.
Do not suppress a warning from this rule unless it is certain that the layout of the type and its base types will not change in a future version.
The following example shows a class that violates the rule and a re-declaration of the class to use an explicit interface.
CA1403: Auto layout types should not be COM visible
CA1412: Mark ComSource Interfaces as IDispatch
Introducing the Class Interface
Qualifying .NET Types for Interoperation
Interoperating with Unmanaged Code