CA1409: Com visible types should be creatable
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
| Item | Value |
|---|---|
| RuleId | CA1409 |
| Category | Microsoft.Interoperability |
| Breaking change | Non-breaking |
Cause
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.
Rule description
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.
How to fix violations
To fix a violation of this rule, add a public default constructor or remove the System.Runtime.InteropServices.ComVisibleAttribute from the type.
When to suppress warnings
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.
Related rules
CA1017: Mark assemblies with ComVisibleAttribute