S2156 — "sealed" classes should not have "protected" members

Why is this an issue?

The difference between private and protected visibility is that child classes can see and use protected members, but they cannot see private ones. Since a sealed class cannot have children, marking its members protected is confusingly pointless.

Noncompliant code example

public sealed class MySealedClass
{
    protected string name = "Fred";  // Noncompliant
    protected void SetName(string name) // Noncompliant
    {
        // ...
    }
}

Compliant solution

public sealed class MySealedClass
{
    private string name = "Fred";
    public void SetName(string name)
    {
        // ...
    }
}