Mutable fields should not be "public static"

https://rules.sonarsource.com/csharp/RSPEC-2386

https://github.com/SonarSource/sonar-dotnet/issues/3636

 public class CustomHelper
    {
        public static List<string> MandatoryFields = new List<string>
        {
            "First name",
            "Last name"
        };
    }

修改为，需要引用

https://docs.microsoft.com/en-us/dotnet/api/system.collections.immutable.immutablelist.create?view=netcore-3.1

  public class CustomHelper
    {
        public static IImmutableList<string> MandatoryFields = ImmutableList.Create(
            "First name",
            "Last name"
        );
    }

public static mutable fields of classes which are accessed directly should be protected to the degree possible. This can be done by reducing the accessibility of the field or by changing the return type to an immutable type.

This rule raises issues for public static fields with a type inheriting/implementing System.Array or System.Collections.Generic.ICollection<T>.

No issue is reported:

• If the type of the field inherits/implements one (at least) of the following types:
  • System.Collections.ObjectModel.ReadOnlyCollection<T>
  • System.Collections.ObjectModel.ReadOnlyDictionary<TKey, TValue>
  • System.Collections.Immutable.IImmutableArray<T>
  • System.Collections.Immutable.IImmutableDictionary<TKey, TValue>
  • System.Collections.Immutable.IImmutableList<T>
  • System.Collections.Immutable.IImmutableSet<T>
  • System.Collections.Immutable.IImmutableStack<T>
  • System.Collections.Immutable.IImmutableQueue<T>
• If the field is readonly and is initialized inline with an immutable type (i.e. inherits/implements one of the types in the previous list) or null. 

原文：https://www.cnblogs.com/chucklu/p/13754685.html