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CA1017: Mark assemblies with ComVisibleAttribute

  • Article
Property Value
Rule ID CA1017
Title Mark assemblies with ComVisibleAttribute
Category Design
Fix is breaking or non-breaking Non-breaking
Enabled by default in .NET 8 No

Cause

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 a whole 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 suppress warnings

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

Example

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

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

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

See also