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Mark assemblies with ComVisible







Breaking Change



An assembly does not have the System.Runtime.InteropServices.ComVisibleAttribute attribute applied to it.

Rule Description

The ComVisibleAttribute attribute determines how COM clients access managed code. Good design dictates that assemblies explicitly indicate COM visibility. COM visibility can be set for an entire assembly and then overridden for individual types and type members. If the attribute is not present, the contents of the assembly are visible to COM clients.

How to Fix Violations

To fix a violation of this rule, add the attribute to the assembly. If you do not want the assembly to be visible to COM clients, apply the attribute and set its value to false.

When to Exclude Warnings

Do not exclude a warning from this rule. If you want the assembly to be visible, apply the attribute and set its value to true.


The following example shows an assembly with the ComVisibleAttribute attribute applied to prevent it from being visible to COM clients.

Imports System

<Assembly: System.Runtime.InteropServices.ComVisible(False)>
Namespace DesignLibrary
End Namespace
using System;

[assembly: System.Runtime.InteropServices.ComVisible(false)]
namespace DesignLibrary {}
using namespace System;

[assembly: System::Runtime::InteropServices::ComVisible(false)];
namespace DesignLibrary {}

See Also


Qualifying .NET Types for Interoperation

Other Resources

Interoperating with Unmanaged Code