1. We have some table TABLE1 contains one column ID (int)
2. Open 2 connections in different threads
3. Connection 1 - select some data from TABLE1, then close
4. Connection 2 - changes structure of TABLE1 adding column COL_1 (any type)
5. Connection 1 (open new)
6. Connection 2 - close
7. Connection 1 - insert data in TABLE1, gets error

Here is sample Code for console application:


using System;
using System.Collections.Generic;
using System.Text;
using FirebirdSql.Data.FirebirdClient;
using System.Threading;

namespace ConsoleApplication1
{
    class Program
    {
        static FbConnectionStringBuilder fbcs;
        static FbConnection cn1;
        static FbConnection cn2;
        static ManualResetEvent e1 = new ManualResetEvent(false);
        static ManualResetEvent e2 = new ManualResetEvent(false);
        static ManualResetEvent e3 = new ManualResetEvent(false);

        static void Main(string[] args)
        {
            fbcs = new FbConnectionStringBuilder();
            fbcs.ServerType = FbServerType.Default;
            fbcs.Database = @"C:\Temp\base.fdb"; //Path to sample DB
            fbcs.DataSource = "localhost";
            fbcs.Dialect = 3;
            fbcs.UserID = "SYSDBA";
            fbcs.Password = "masterkey";

            ThreadPool.QueueUserWorkItem(new WaitCallback(StartConnectionOne));
            ThreadPool.QueueUserWorkItem(new WaitCallback(DoInThread));

            Thread.Sleep(1000);

            e1.Set();

            Console.Read();
        }

        static void StartConnectionOne(object state)
        {
            cn1 = new FbConnection(fbcs.ConnectionString);
            cn1.Open();

            e2.WaitOne();

            using (var cmd = cn1.CreateCommand())
            {
                cmd.Transaction = cn1.BeginTransaction();

                try
                {
                    Console.WriteLine("Alter");
                    cmd.CommandText = "alter table TABLE1 add COL_1 varchar(255)";

                    cmd.ExecuteNonQuery();

                    cmd.Transaction.Commit();
                    Console.WriteLine("Alter success");
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Alter error: " + ex.Message);
                    cmd.Transaction.Rollback();
                }
            }

            e3.Set();

        }

        static void DoInThread(object state)
        {
            cn2 = new FbConnection(fbcs.ConnectionString);
            cn2.Open();

            e1.WaitOne();

            using (var cmd = cn2.CreateCommand())
            {
                try
                {
                    Console.WriteLine("Select 1");
                    cmd.CommandText = "select * from TABLE1 order by ID";

                    using (var r = cmd.ExecuteReader())
                    {
                        while (r.Read())
                        {
                            Console.WriteLine(r.ToString());
                        }
                    }
                    Console.WriteLine("Select 1 success");
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Select 1 error: " + ex.Message);
                }
            }

            cn2.Close();
            cn2.Dispose();

            e2.Set();

            e3.WaitOne();

            cn2 = new FbConnection(fbcs.ConnectionString);
            cn2.Open();

            cn1.Close();
            cn1.Dispose();

            using (var cmd = cn2.CreateCommand())
            {
                try
                {
                    Console.WriteLine("Select 2");
                    cmd.CommandText = "select * from TABLE1 order by COL_1";

                    using (var r = cmd.ExecuteReader())
                    {
                        while (r.Read())
                        {
                            Console.WriteLine(r.ToString());
                        }
                    }
                    Console.WriteLine("Select 2 success");
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Select 2 error: " + ex.Message);
                }
            }

            using (var cmd = cn2.CreateCommand())
            {
                cmd.Transaction = cn2.BeginTransaction();

                try
                {
                    Console.WriteLine("Insert");
                    cmd.CommandText = "insert into TABLE1 (ID, COL_1) Values (1, '1234')";
                    
                    cmd.ExecuteNonQuery();

                    cmd.Transaction.Commit();
                    Console.WriteLine("Insert success");
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Insert error: " + ex.Message);
                    cmd.Transaction.Rollback();
                }
            }
        }
    }
}