System.Data.SQLite

namespace System.Data.SQLite
{
    using System;
    using System.Data;
    using System.Data.Common;
    using System.Threading;

    ///////////////////////////////////////////////////////////////////////////////////////////////

    /// <summary>
    /// SQLite implementation of DbTransaction.
    /// </summary>
    public sealed class SQLiteTransaction : DbTransaction
    {
        /// <summary>
        /// The connection to which this transaction is bound
        /// </summary>
        internal SQLiteConnection _cnn;

        /// <summary>
        internal int _version; // Matches the version of the connection
        /// Matches the version of the connection.
        /// </summary>
        private int _version;

        /// <summary>
        /// The isolation level for this transaction.
        /// </summary>
        private IsolationLevel _level;

        ///////////////////////////////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Constructs the transaction object, binding it to the supplied connection
        /// </summary>
        /// <param name="connection">The connection to open a transaction on</param>
        /// <param name="deferredLock">TRUE to defer the writelock, or FALSE to lock immediately</param>
        internal SQLiteTransaction(SQLiteConnection connection, bool deferredLock)

                    cmd.ExecuteNonQuery();
                }
            }
            _cnn._transactionLevel--;
            _cnn = null;
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Returns the underlying connection to which this transaction applies.
        /// </summary>
        public new SQLiteConnection Connection
        {
            get { CheckDisposed(); return _cnn; }
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Forwards to the local Connection property
        /// </summary>
        protected override DbConnection DbConnection
        {
            get { return Connection; }
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets the isolation level of the transaction.  SQLite only supports Serializable transactions.
        /// </summary>
        public override IsolationLevel IsolationLevel
        {
            get { CheckDisposed(); return _level; }
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Rolls back the active transaction.
        /// </summary>
        public override void Rollback()
        {
            CheckDisposed();
            SQLiteConnection.Check(_cnn);
            IsValid(true);
            IssueRollback(true);
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////

        internal void IssueRollback(bool throwError)
        {
            SQLiteConnection cnn = Interlocked.Exchange(ref _cnn, null);

            if (cnn != null)
            {

                {
                    if (throwError)
                        throw;
                }
                cnn._transactionLevel = 0;
            }
        }

        ///////////////////////////////////////////////////////////////////////////////////////////////

        internal bool IsValid(bool throwError)
        {
            if (_cnn == null)
            {
                if (throwError == true) throw new ArgumentNullException("No connection associated with this transaction");
                else return false;