<PackageReference Include="System.Text.Encoding.CodePages" Version="8.0.0-preview.2.23128.3" />

MaybeNullWhenAttribute

Specifies that when a method returns ReturnValue, the parameter may be null even if the corresponding type disallows it.
namespace System.Diagnostics.CodeAnalysis { [AttributeUsage(AttributeTargets.Parameter, Inherited = false)] internal sealed class MaybeNullWhenAttribute : Attribute { public bool ReturnValue { get; } public MaybeNullWhenAttribute(bool returnValue) { ReturnValue = returnValue; } } }