<PackageReference Include="Microsoft.Data.SqlClient" Version="7.0.2" />

Microsoft.Data.SqlClient.ConnectionPool.ConnectionPoolSlots

sealed class ConnectionPoolSlots
A thread-safe collection with a fixed capacity. Avoids wasted work by reserving a slot before adding an item.
namespace Microsoft.Data.SqlClient.ConnectionPool { internal sealed class ConnectionPoolSlots { internal delegate DbConnectionInternal CreateCallback (); internal delegate void CleanupCallback (DbConnectionInternal connection); } }