C# – SQL not available after a failed insert with NHibernate

I have an integration test that tries to insert a row with a column that is a duplicate of a unique column that another row has. To insert the row, I call this code which is found in my entities repository:

using (var transaction = rb.unitOfWork.Session.BeginTransaction())
        {
            try
            {
                ret = (Key)rb.unitOfWork.Session.Save(entity);
                transaction.Commit();
                rb.unitOfWork.Session.Clear();
            }
            catch
            {
                transaction.Rollback();
                rb.unitOfWork.Session.Clear();
                throw;
            }
        }

When this code is run with the duplicate entity, I can see the insert come through on NHibernate Profiler. Right after that statement, I see these warnings and errors:

— statement #1
WARN:
System.Data.SqlClient.SqlException (0x80131904): Violation of UNIQUE KEY constraint 'UQ_Contract_C51D43DA5070F446'. Cannot insert duplicate key in object 'dbo.Contracts'. The duplicate key value is (1005171).
The statement has been terminated.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning()
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at System.Data.SqlClient.SqlCommand.ExecuteBatchRPCCommand()
at System.Data.SqlClient.SqlCommandSet.ExecuteNonQuery()
at NHibernate.AdoNet.SqlClientSqlCommandSet.ExecuteNonQuery()
at NHibernate.AdoNet.SqlClientBatchingBatcher.DoExecuteBatch(IDbCommand ps)

— statement #2
ERROR:
Violation of UNIQUE KEY constraint 'UQ_Contract_C51D43DA5070F446'. Cannot insert duplicate key in object 'dbo.Contracts'. The duplicate key value is (1005171).
The statement has been terminated.

— statement #3
ERROR:
could not execute batch command.[SQL: SQL not available]Could not synchronize database state with session

— statement #4
rollback transaction

After this test, I do a lot of Query testing and everything seems to be working fine until I hit an update statement for the same repository. Here is the code that gets called:

using (var transaction = rb.unitOfWork.Session.BeginTransaction())
        {
            rb.unitOfWork.Session.SaveOrUpdate(entity);
            transaction.Commit();
            rb.unitOfWork.Session.Clear();
        }
        rb.unitOfWork.Session.Evict(entity);

Checking the profiler shows that the update gets called, bur right after that, I get these statements:

— statement #1
WARN:
System.Data.SqlClient.SqlException (0x80131904): Violation of UNIQUE KEY constraint 'UQ_Contract_C51D43DA5070F446'. Cannot insert duplicate key in object 'dbo.Contracts'. The duplicate key value is (1005171).
The statement has been terminated.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning()
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at System.Data.SqlClient.SqlCommand.ExecuteBatchRPCCommand()
at System.Data.SqlClient.SqlCommandSet.ExecuteNonQuery()
at NHibernate.AdoNet.SqlClientSqlCommandSet.ExecuteNonQuery()
at NHibernate.AdoNet.SqlClientBatchingBatcher.DoExecuteBatch(IDbCommand ps)

— statement #2
ERROR:
Violation of UNIQUE KEY constraint 'UQ_Contract_C51D43DA5070F446'. Cannot insert duplicate key in object 'dbo.Contracts'. The duplicate key value is (1005171).
The statement has been terminated.

— statement #3
ERROR:
could not execute batch command.[SQL: SQL not available]Could not synchronize database state with session

From what I can see, it seems like the insert statement put NHibernate into a failed state. The update code above throws a GenericADOException that says SQL Not Available. I must be doing something wrong here. Should I be handling the exception differently?