CA1401: P/Invokes should not be visible

Cause

A public or protected method in a public type has the System.Runtime.InteropServices.DllImportAttribute attribute (also implemented by the Declare keyword in Visual Basic).

Rule Description

Methods that are marked with the DllImportAttribute attribute (or methods that are defined by using the Declare keyword in Visual Basic) use Platform Invocation Services to access unmanaged code. Such methods should not be exposed. By keeping these methods private or internal, you make sure that your library cannot be used to breach security by allowing callers access to unmanaged APIs that they could not call otherwise.

How to Fix Violations

To fix a violation of this rule, change the access level of the method.

When to Suppress Warnings

Do not suppress a warning from this rule.

Example

The following example declares a method that violates this rule.

Imports System

NameSpace MSInternalLibrary

' Violates rule: PInvokesShouldNotBeVisible.
Public Class NativeMethods
    Public Declare Function RemoveDirectory Lib "kernel32"( _
        ByVal Name As String) As Boolean
End Class

End NameSpace 

using System;
using System.Runtime.InteropServices;

namespace InteroperabilityLibrary
{
    // Violates rule: PInvokesShouldNotBeVisible.
    public class NativeMethods
    {
        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
        public static extern bool RemoveDirectory(string name);
    }
}