diff --git a/src/NHibernate/Async/Transaction/AdoNetTransactionFactory.cs b/src/NHibernate/Async/Transaction/AdoNetTransactionFactory.cs
index ec3ea6bc578..76466173109 100644
--- a/src/NHibernate/Async/Transaction/AdoNetTransactionFactory.cs
+++ b/src/NHibernate/Async/Transaction/AdoNetTransactionFactory.cs
@@ -16,7 +16,6 @@
 using NHibernate.Engine;
 using NHibernate.Engine.Transaction;
 using NHibernate.Exceptions;
-using NHibernate.Impl;
 
 namespace NHibernate.Transaction
 {
@@ -42,25 +41,17 @@ async Task InternalExecuteWorkInIsolationAsync()
 
 				DbConnection connection = null;
 				DbTransaction trans = null;
-				// bool wasAutoCommit = false;
 				try
 				{
 					// We make an exception for SQLite and use the session's connection,
 					// since SQLite only allows one connection to the database.
-					if (session.Factory.Dialect is SQLiteDialect)
-						connection = session.Connection;
-					else
-						connection = await (session.Factory.ConnectionProvider.GetConnectionAsync(cancellationToken)).ConfigureAwait(false);
+					connection = session.Factory.Dialect is SQLiteDialect
+					? session.Connection
+					: await (session.Factory.ConnectionProvider.GetConnectionAsync(cancellationToken)).ConfigureAwait(false);
 
 					if (transacted)
 					{
 						trans = connection.BeginTransaction();
-						// TODO NH: a way to read the autocommit state is needed
-						//if (TransactionManager.GetAutoCommit(connection))
-						//{
-						//  wasAutoCommit = true;
-						//  TransactionManager.SetAutoCommit(connection, false);
-						//}
 					}
 
 					await (work.DoWorkAsync(connection, trans, cancellationToken)).ConfigureAwait(false);
@@ -68,7 +59,6 @@ async Task InternalExecuteWorkInIsolationAsync()
 					if (transacted)
 					{
 						trans.Commit();
-						//TransactionManager.Commit(connection);
 					}
 				}
 				catch (Exception t)
@@ -84,49 +74,33 @@ async Task InternalExecuteWorkInIsolationAsync()
 						}
 						catch (Exception ignore)
 						{
-							isolaterLog.Debug(ignore, "Unable to rollback transaction");
+							_isolatorLog.Debug(ignore, "Unable to rollback transaction");
 						}
 
-						if (t is HibernateException)
-						{
-							throw;
-						}
-						else if (t is DbException)
-						{
-							throw ADOExceptionHelper.Convert(session.Factory.SQLExceptionConverter, t,
-						                                 "error performing isolated work");
-						}
-						else
-						{
-							throw new HibernateException("error performing isolated work", t);
-						}
+						switch (t)
+					{
+						case HibernateException _:
+								throw;
+						case DbException _:
+								throw ADOExceptionHelper.Convert(session.Factory.SQLExceptionConverter, t,
+							                                 "error performing isolated work");
+						default:
+								throw new HibernateException("error performing isolated work", t);
+					}
 					}
 				}
 				finally
 				{
-					//if (transacted && wasAutoCommit)
-					//{
-					//  try
-					//  {
-					//    // TODO NH: reset autocommit
-					//    // TransactionManager.SetAutoCommit(connection, true);
-					//  }
-					//  catch (Exception)
-					//  {
-					//    log.Debug("was unable to reset connection back to auto-commit");
-					//  }
-					//}
-
 					try
 					{
 						trans?.Dispose();
 					}
 					catch (Exception ignore)
 					{
-						isolaterLog.Warn(ignore, "Unable to dispose transaction");
+						_isolatorLog.Warn(ignore, "Unable to dispose transaction");
 					}
 
-					if (session.Factory.Dialect is SQLiteDialect == false)
+					if (connection != null && session.Factory.Dialect is SQLiteDialect == false)
 						session.Factory.ConnectionProvider.CloseConnection(connection);
 				}
 			}
diff --git a/src/NHibernate/Connection/ConnectionProvider.cs b/src/NHibernate/Connection/ConnectionProvider.cs
index a49012c1262..e30c2fdf21d 100644
--- a/src/NHibernate/Connection/ConnectionProvider.cs
+++ b/src/NHibernate/Connection/ConnectionProvider.cs
@@ -24,6 +24,9 @@ public abstract partial class ConnectionProvider : IConnectionProvider
 		/// <param name="conn">The <see cref="DbConnection"/> to clean up.</param>
 		public virtual void CloseConnection(DbConnection conn)
 		{
+			if (conn == null)
+				throw new ArgumentNullException(nameof(conn));
+
 			log.Debug("Closing connection");
 			try
 			{
diff --git a/src/NHibernate/Transaction/AdoNetTransactionFactory.cs b/src/NHibernate/Transaction/AdoNetTransactionFactory.cs
index e1d485aeecb..5fe50f06757 100644
--- a/src/NHibernate/Transaction/AdoNetTransactionFactory.cs
+++ b/src/NHibernate/Transaction/AdoNetTransactionFactory.cs
@@ -6,7 +6,6 @@
 using NHibernate.Engine;
 using NHibernate.Engine.Transaction;
 using NHibernate.Exceptions;
-using NHibernate.Impl;
 
 namespace NHibernate.Transaction
 {
@@ -16,7 +15,7 @@ namespace NHibernate.Transaction
 	/// </summary>
 	public partial class AdoNetTransactionFactory : ITransactionFactory
 	{
-		private readonly INHibernateLogger isolaterLog = NHibernateLogger.For(typeof(ITransactionFactory));
+		private static readonly INHibernateLogger _isolatorLog = NHibernateLogger.For(typeof(ITransactionFactory));
 
 		/// <inheritdoc />
 		public virtual ITransaction CreateTransaction(ISessionImplementor session)
@@ -52,25 +51,17 @@ public virtual void ExecuteWorkInIsolation(ISessionImplementor session, IIsolate
 
 			DbConnection connection = null;
 			DbTransaction trans = null;
-			// bool wasAutoCommit = false;
 			try
 			{
 				// We make an exception for SQLite and use the session's connection,
 				// since SQLite only allows one connection to the database.
-				if (session.Factory.Dialect is SQLiteDialect)
-					connection = session.Connection;
-				else
-					connection = session.Factory.ConnectionProvider.GetConnection();
+				connection = session.Factory.Dialect is SQLiteDialect
+					? session.Connection
+					: session.Factory.ConnectionProvider.GetConnection();
 
 				if (transacted)
 				{
 					trans = connection.BeginTransaction();
-					// TODO NH: a way to read the autocommit state is needed
-					//if (TransactionManager.GetAutoCommit(connection))
-					//{
-					//  wasAutoCommit = true;
-					//  TransactionManager.SetAutoCommit(connection, false);
-					//}
 				}
 
 				work.DoWork(connection, trans);
@@ -78,7 +69,6 @@ public virtual void ExecuteWorkInIsolation(ISessionImplementor session, IIsolate
 				if (transacted)
 				{
 					trans.Commit();
-					//TransactionManager.Commit(connection);
 				}
 			}
 			catch (Exception t)
@@ -94,49 +84,33 @@ public virtual void ExecuteWorkInIsolation(ISessionImplementor session, IIsolate
 					}
 					catch (Exception ignore)
 					{
-						isolaterLog.Debug(ignore, "Unable to rollback transaction");
+						_isolatorLog.Debug(ignore, "Unable to rollback transaction");
 					}
 
-					if (t is HibernateException)
+					switch (t)
 					{
-						throw;
-					}
-					else if (t is DbException)
-					{
-						throw ADOExceptionHelper.Convert(session.Factory.SQLExceptionConverter, t,
-						                                 "error performing isolated work");
-					}
-					else
-					{
-						throw new HibernateException("error performing isolated work", t);
+						case HibernateException _:
+							throw;
+						case DbException _:
+							throw ADOExceptionHelper.Convert(session.Factory.SQLExceptionConverter, t,
+							                                 "error performing isolated work");
+						default:
+							throw new HibernateException("error performing isolated work", t);
 					}
 				}
 			}
 			finally
 			{
-				//if (transacted && wasAutoCommit)
-				//{
-				//  try
-				//  {
-				//    // TODO NH: reset autocommit
-				//    // TransactionManager.SetAutoCommit(connection, true);
-				//  }
-				//  catch (Exception)
-				//  {
-				//    log.Debug("was unable to reset connection back to auto-commit");
-				//  }
-				//}
-
 				try
 				{
 					trans?.Dispose();
 				}
 				catch (Exception ignore)
 				{
-					isolaterLog.Warn(ignore, "Unable to dispose transaction");
+					_isolatorLog.Warn(ignore, "Unable to dispose transaction");
 				}
 
-				if (session.Factory.Dialect is SQLiteDialect == false)
+				if (connection != null && session.Factory.Dialect is SQLiteDialect == false)
 					session.Factory.ConnectionProvider.CloseConnection(connection);
 			}
 		}