I have created a temporary table with an npgsql command and if there is an error in my code, after I cannot find my temporary table! I know that postgres don’t drop temporary table inside the connection but only when I close the connection.
This is a sample test code:

try {
                //___
                var connectionString_log = new NpgsqlConnectionStringBuilder
                {
                    Host = "127.0.0.1",
                    Database = "bracciniRRSNET",
                    Username = "dba",
                    Password = "sql",
                    Port = 5432,
                    Pooling = false,

                    ApplicationName = "NewRRSNpgsqlClient", //ConnectionInfo.ApplicationName,       Questo è nel token!
                    IncludeErrorDetail = true
                }.ConnectionString;
                 
               
                var connection = new NpgsqlConnection(connectionString_log);
                {
                    connection.Open();
                    var transaction = connection.BeginTransaction();
                    var command = new NpgsqlCommand("", connection, transaction:transaction);
//Create a temporary table and insert some records.
                    command.CommandText = @"CREATE TEMP TABLE temp_users(
                                                user_id SERIAL PRIMARY KEY,
                                                username VARCHAR(50) NOT NULL,
                                                email VARCHAR(100) NOT NULL
                                            )  ON COMMIT PRESERVE ROWS;INSERT INTO temp_users (username, email) VALUES ('Alice', '[email protected]');
                                              INSERT INTO temp_users (username, email) VALUES ('Bob', '[email protected]');";
                                command.ExecuteNonQuery();

                                var sql_copy = $"COPY delstory to STDout BINARY;";
                                command.CommandText = sql_copy;


                                byte[] buffer = new byte[100 * 1024 * 1024];
                                MemoryStream memoryStream = new MemoryStream();

                                using (var outStream = await connection.BeginRawBinaryCopyAsync(sql_copy))
                                {
                                    int bytesRead;
`your text`
                                    while ((bytesRead = await outStream.ReadAsync(buffer, 0, buffer.Length)) > 0)
                                    {
                                        memoryStream.Write(buffer, 0, bytesRead);
                                    }

                                }
                                memoryStream.Seek(0, SeekOrigin.Begin);

                                try
                                {
                                    //Now do a duplicate key error.....
                                    var copy = $"COPY delstory from  STDin BINARY";
                                    command.CommandText = copy;  
                                    using (var outStream = await connection.BeginRawBinaryCopyAsync(copy))
                                    {

                                        int bytesRead;
                                        while ((bytesRead = memoryStream.Read(buffer, 0, buffer.Length)) > 0)
                                        {
                                            await outStream.WriteAsync(buffer, 0, bytesRead);
                                        }

                                        outStream.Write(buffer);
                                    }
                                }
                                catch (Exception ex)
                                {   
                                    if (ex.Message.Contains("23505:")) // Duplicated error catch
                                    {
                                        try
                                        {
                                            transaction.Commit(); //Close transaction that's blocked
                                            transaction = connection.BeginTransaction();
                                            command = new NpgsqlCommand("", connection, transaction: transaction);
                                            command.CommandText = "select count(*) from temp_users;"; // Cannot find temp_users!
                                            var reader = await command.ExecuteReaderAsync();
                                            reader.Read();
                                            Console.WriteLine(ex.Message);
                                        }
                                        catch (Exception ex2)
                                        {
                                            Console.WriteLine(ex2.Message);
                                        }
                             
                                    }
                                }

                                connection.Close();


                }

            } 
            catch (Exception ex) { Console.WriteLine(ex.Message); }

Output: 42P01: relation “temp_users” does not exist

Where is my mistake ?

Why the table is out ?