using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Text;

namespace Concurrency
{
    public class Deadlocker : IDisposable
    {
        private readonly SqlConnection _anotherConnection;
        private readonly SqlCommand _command;
        private readonly SqlCommand _anotherCommand;
        private readonly IAsyncResult _anotherCommandStarted;

        public Deadlocker(SqlConnection connection, string hookCommand)
        {
            _command = connection.CreateCommand();
            _command.CommandText = "SET DEADLOCK_PRIORITY LOW; BEGIN TRANSACTION; UPDATE Data.Hook1 SET i=1-i;";
            _command.CommandType = CommandType.Text;
            _command.ExecuteNonQuery();
            _anotherConnection = new SqlConnection(connection.ConnectionString + ";Asynchronous Processing=true");
            _anotherConnection.Open();
            _anotherCommand = _anotherConnection.CreateCommand();
            _anotherCommand.CommandText = string.Format("SET DEADLOCK_PRIORITY HIGH; BEGIN TRANSACTION; {0};", hookCommand);
            _anotherCommand.CommandType = CommandType.Text;
            _anotherCommand.ExecuteNonQuery();
            _anotherCommand.CommandText = "UPDATE Data.Hook1 SET i=1-i";
            _anotherCommandStarted =  _anotherCommand.BeginExecuteNonQuery();
        }

        public void Dispose()
        {
            _command.CommandText = "IF @@TRANCOUNT>0 BEGIN ROLLBACK; END";
            _command.ExecuteNonQuery();
            _anotherCommand.EndExecuteNonQuery(_anotherCommandStarted);
            _anotherCommand.CommandText = _command.CommandText;
            _anotherCommand.ExecuteNonQuery();
            _anotherConnection.Close();
        }
    }
}