Do not use Optional on ref or out. parameters

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Metadata

ID: csharp-best-practices/optional-ref-out

Language: C#

Severity: Info

Category: Best Practices

Description

The modifier Optional should not be used on ref or out parameters because it’s semantically incorrect:

  • an out parameter is used as a value to return from the function and, therefore, is not optional
  • a ref parameter is passed back to the caller

Non-Compliant Code Examples

class MyClass {

    public static void routine([Optional] out i)
    {
    }
}
class MyClass {
    public static void routine([Optional] ref int i)
    {
    }

}
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