<PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.0-preview.5.25277.114" />

System.Diagnostics.CodeAnalysis.MemberNotNullWhenAttribute

Specifies that the method or property will ensure that the listed field and property members have not-null values when returning with the specified return value condition.
namespace System.Diagnostics.CodeAnalysis { internal sealed class MemberNotNullWhenAttribute : Attribute { public bool ReturnValue { get; } public string[] Members { get; } public MemberNotNullWhenAttribute(bool returnValue, string member); public MemberNotNullWhenAttribute(bool returnValue, params string[] members); } }