CA1420: Property, type, or attribute requires runtime marshalling

Property	Value
Rule ID	CA1420
Title	Property, type, or attribute requires runtime marshalling
Category	Interoperability
Fix is breaking or non-breaking	Breaking
Enabled by default in .NET 9	As warning

Cause

A code feature is used that requires runtime marshalling, and runtime marshalling is explicitly disabled.

Rule description

Using features that require runtime marshalling when runtime marshalling is disabled will result in run-time exceptions.

How to fix violations

Enable runtime marshalling or remove the code that requires runtime marshalling.

When to suppress warnings

Don't suppress a warning from this rule.

Example

The following code snippet shows a violation of CA1420:

using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

[assembly: DisableRuntimeMarshalling]

class C
{
    // Violates rule CA1420.
    [DllImport("NativeLibrary", SetLastError = true)]
    public static extern void MyMethod ();
}

Imports System.Runtime.InteropServices
Imports System.Runtime.CompilerServices

<Assembly: DisableRuntimeMarshalling>

Class C
    ' Violates rule CA1420.
    <DllImport("NativeLibrary", SetLastError:=True)>
    Public Shared Sub MyMethod()
        '...
    End Sub
End Class

To fix the violation, remove the DisableRuntimeMarshallingAttribute on the assembly.