<PackageReference Include="System.ClientModel" Version="1.7.0" />

System.ClientModel.Internal.BitVector640

struct BitVector640
This type effectively stores 640 bool values, but compresses their storage into ten ulongs, where each bit of the ulong represents a single bool value. It exposes a public indexer so that the bool values can be accessed as a standard .NET collection API. It is used in System.ClientModel and Azure.Core to implement response classifiers, where each true bit represents a status code that the classifier considers a success code.
namespace System.ClientModel.Internal { internal struct BitVector640 { public bool this[int i] { [System.Runtime.CompilerServices.IsReadOnly] get; set; } } }