public SqlServerSpecializations(ConnectionService connectionService)
 {
     _conService = connectionService ??
                   throw new ArgumentNullException(nameof(connectionService));
 }
 public SqlServerDoctors(ConnectionService connectionService)
 {
     _conService = connectionService
                   ?? throw new ArgumentNullException(nameof(connectionService));
 }
 public SqlServerHealthGroups(ConnectionService connectionService)
 {
     _conService = connectionService ??
                   throw new ArgumentNullException(nameof(connectionService));
 }