COM registration methods should not be visible

Cause

A method marked with the System.Runtime.InteropServices.ComRegisterFunctionAttribute or the System.Runtime.InteropServices.ComUnregisterFunctionAttribute attribute is externally visible.

Rule Description

When an assembly is registered with COM, entries are added to the registry for each of the COM visible types in the assembly. Methods marked with the ComRegisterFunctionAttribute and ComUnregisterFunctionAttribute attributes are called during the registration and unregistration processes, respectively, to run user code that is specific to the registration/unregistration of these types. This code should not called outside these processes.

How to Fix Violations

To fix a violation of this rule change the accessibility of the method to private or internal (Friend in Visual Basic).

When to Suppress Warnings

Do not suppress a warning from this rule.

Example

The following example shows two methods that violate the rule.

Imports System
Imports System.Runtime.InteropServices

<Assembly: ComVisibleAttribute(True)>
Namespace InteroperabilityLibrary

   Public Class ClassToRegister
   End Class 

   Public Class ComRegistration

      <ComRegisterFunctionAttribute> _ 
      Public Shared Sub RegisterFunction(typeToRegister As Type)
      End Sub

      <ComUnregisterFunctionAttribute> _ 
      Public Shared Sub UnregisterFunction(typeToRegister As Type)
      End Sub 

   End Class 

End Namespace

using System;
using System.Runtime.InteropServices;

[assembly: ComVisible(true)]
namespace InteroperabilityLibrary
{
   public class ClassToRegister
   {
   }

   public class ComRegistration
   {
      [ComRegisterFunction]
      public static void RegisterFunction(Type typeToRegister) {}

      [ComUnregisterFunction]
      public static void UnregisterFunction(Type typeToRegister) {}
   }
}

Related Rules

COM registration methods should be matched

See Also

Concepts

Registering Assemblies with COM

Reference

Assembly Registration Tool (Regasm.exe)

System.Runtime.InteropServices.RegistrationServices