CA1409: Com visible types should be creatable


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The latest version of this topic can be found at CA1409: Com visible types should be creatable.

|Breaking Change|Non-breaking|

A reference type that is specifically marked as visible to Component Object Model (COM) contains a public parameterized constructor but does not contain a public default (parameterless) constructor.

A type without a public default constructor cannot be created by COM clients. However, the type can still be accessed by COM clients if another means is available to create the type and pass it to the client (for example, through the return value of a method call).

The rule ignores types that are derived from System.Delegate.

By default, the following are visible to COM: assemblies, public types, public instance members in public types, and all members of public value types.

To fix a violation of this rule, add a public default constructor or remove the System.Runtime.InteropServices.ComVisibleAttribute from the type.

It is safe to suppress a warning from this rule if other ways are provided to create and pass the object to the COM client.

CA1017: Mark assemblies with ComVisibleAttribute

Qualifying .NET Types for Interoperation
Interoperating with Unmanaged Code