/// <summary>
    /// Initializes the statement and attempts to get all information about parameters in the statement
    /// </summary>
    /// <param name="sqlbase">The base SQLite object</param>
    /// <param name="flags">The flags associated with the parent connection object</param>
    /// <param name="stmt">The statement</param>
    /// <param name="strCommand">The command text for this statement</param>
    /// <param name="previous">The previous command in a multi-statement command</param>
    internal SQLiteStatement(SQLiteBase sqlbase, SQLiteConnectionFlags flags, SQLiteStatementHandle stmt, string strCommand, SQLiteStatement previous)
    {
      _sql     = sqlbase;
      _sqlite_stmt = stmt;
      _sqlStatement  = strCommand;
      _flags = flags;

      // Determine parameters for this statement (if any) and prepare space for them.
      int nCmdStart = 0;
      int n = _sql.Bind_ParamCount(this, _flags);
      int x;
      string s;

      if (n > 0)
      {
        if (previous != null)
          nCmdStart = previous._unnamedParameters;

        _paramNames = new string[n];
        _paramValues = new SQLiteParameter[n];

        for (x = 0; x < n; x++)
        {
          s = _sql.Bind_ParamName(this, _flags, x + 1);
          if (String.IsNullOrEmpty(s))
          {
            s = String.Format(CultureInfo.InvariantCulture, ";{0}", nCmdStart);
            nCmdStart++;
            _unnamedParameters++;
          }
          _paramNames[x] = s;
          _paramValues[x] = null;
        }
      }
    }

    internal override string Bind_ParamName(SQLiteStatement stmt, SQLiteConnectionFlags flags, int index)
    {
        SQLiteStatementHandle handle = stmt._sqlite_stmt;
        string name;

#if !SQLITE_STANDARD
        int len;
        name = UTF8ToString(UnsafeNativeMethods.sqlite3_bind_parameter_name_interop(handle, index, out len), len);
#else
        name = UTF8ToString(UnsafeNativeMethods.sqlite3_bind_parameter_name(handle, index), -1);
#endif

#if !PLATFORM_COMPACTFRAMEWORK
        if ((flags & SQLiteConnectionFlags.LogBind) == SQLiteConnectionFlags.LogBind)
        {
            //IntPtr handleIntPtr = handle;

            //SQLiteLog.LogMessage(0, String.Format(
            //    "Statement {0} paramter #{1} name is {{{2}}}.",
            //    handleIntPtr, index, name));
        }
#endif

        return name;
    }

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

    /// <summary>
    /// Placeholder for a user-defined disposal routine
    /// </summary>
    /// <param name="disposing">True if the object is being disposed explicitly</param>
    protected virtual void Dispose(bool disposing)
    {
        if (!disposed)
        {
            if (disposing)
            {
                ////////////////////////////////////
                // dispose managed resources here...
                ////////////////////////////////////

                IDisposable disp;

                foreach (KeyValuePair<IntPtr, AggregateData> kv in _contextDataList)
                {
                    disp = kv.Value._data as IDisposable;
                    if (disp != null)
                        disp.Dispose();
                }
                _contextDataList.Clear();
                _contextDataList = null;

                _flags = SQLiteConnectionFlags.None;

                _InvokeFunc = null;
                _StepFunc = null;
                _FinalFunc = null;
                _CompareFunc = null;
                _base = null;
            }

            //////////////////////////////////////
            // release unmanaged resources here...
            //////////////////////////////////////

            disposed = true;
        }
    }

    /// <summary>
    /// Initializes the connection with the specified connection string
    /// </summary>
    /// <param name="connectionString">The connection string to use on the connection</param>
    public SQLiteConnection(string connectionString)
    {
#if (SQLITE_STANDARD || USE_INTEROP_DLL || PLATFORM_COMPACTFRAMEWORK) && PRELOAD_NATIVE_LIBRARY
      UnsafeNativeMethods.Initialize();
#endif

#if !PLATFORM_COMPACTFRAMEWORK
      SQLiteLog.Initialize();
#endif

      _flags = SQLiteConnectionFlags.Default;
      _connectionState = ConnectionState.Closed;
      _connectionString = "";
      //_commandList = new List<WeakReference>();

      if (connectionString != null)
        ConnectionString = connectionString;
    }

    /// <summary>
    /// Initializes the connection with the specified connection string.
    /// </summary>
    /// <param name="connectionString">
    /// The connection string to use.
    /// </param>
    /// <param name="parseViaFramework">
    /// Non-zero to parse the connection string using the built-in (i.e.
    /// framework provided) parser when opening the connection.
    /// </param>
    public SQLiteConnection(string connectionString, bool parseViaFramework)
    {
#if (SQLITE_STANDARD || USE_INTEROP_DLL || PLATFORM_COMPACTFRAMEWORK) && PRELOAD_NATIVE_LIBRARY
      UnsafeNativeMethods.Initialize();
#endif

#if !INTEROP_LOG
      SQLiteLog.Initialize();
#endif

#if !PLATFORM_COMPACTFRAMEWORK && !INTEROP_LEGACY_CLOSE && SQLITE_STANDARD
      //
      // NOTE: Check if the sqlite3_close_v2() native API should be available
      //       to use.  This must be done dynamically because the delegate set
      //       here is used by the SQLiteConnectionHandle class, which is a
      //       CriticalHandle derived class (i.e. protected by a constrained
      //       execution region).  Therefore, if the underlying native entry
      //       point is unavailable, an exception will be raised even if it is
      //       never actually called (i.e. because the runtime eagerly prepares
      //       all the methods in the call graph of the constrained execution
      //       region).
      //
      lock (_syncRoot)
      {
          if (_versionNumber == 0)
          {
              _versionNumber = SQLite3.SQLiteVersionNumber;

              if (_versionNumber >= 3007014)
                  SQLiteConnectionHandle.closeConnection = SQLiteBase.CloseConnectionV2;
          }
      }
#endif

#if INTEROP_LOG
      if (UnsafeNativeMethods.sqlite3_config_log_interop() == SQLiteErrorCode.Ok)
      {
          UnsafeNativeMethods.sqlite3_log(
              SQLiteErrorCode.Ok, SQLiteConvert.ToUTF8("logging initialized."));
      }
#endif

      _parseViaFramework = parseViaFramework;
      _flags = SQLiteConnectionFlags.Default;
      _connectionState = ConnectionState.Closed;
      _connectionString = null;

      if (connectionString != null)
        ConnectionString = connectionString;
    }

    /// <summary>
    /// Opens the connection using the parameters found in the <see cref="ConnectionString" />.
    /// </summary>
    public override void Open()
    {
      CheckDisposed();

      OnChanged(this, new ConnectionEventArgs(
          SQLiteConnectionEventType.Opening, null, null, null, null, null));

      if (_connectionState != ConnectionState.Closed)
        throw new InvalidOperationException();

      Close();

      SortedList<string, string> opts = ParseConnectionString(
          _connectionString, _parseViaFramework);

      OnChanged(this, new ConnectionEventArgs(
          SQLiteConnectionEventType.ConnectionString, null, null, null, _connectionString, opts));

      object enumValue;

      enumValue = TryParseEnum(typeof(SQLiteConnectionFlags), FindKey(opts, "Flags", DefaultFlags.ToString()), true);
      _flags = (enumValue is SQLiteConnectionFlags) ? (SQLiteConnectionFlags)enumValue : DefaultFlags;

      bool fullUri = false;
      string fileName;

      if (Convert.ToInt32(FindKey(opts, "Version", DefaultVersion.ToString()), CultureInfo.InvariantCulture) != DefaultVersion)
        throw new NotSupportedException(String.Format(CultureInfo.CurrentCulture, "Only SQLite Version {0} is supported at this time", DefaultVersion));

      fileName = FindKey(opts, "Data Source", DefaultDataSource);

      if (String.IsNullOrEmpty(fileName))
      {
        fileName = FindKey(opts, "Uri", DefaultUri);
        if (String.IsNullOrEmpty(fileName))
        {
          fileName = FindKey(opts, "FullUri", DefaultFullUri);
          if (String.IsNullOrEmpty(fileName))
            throw new ArgumentException(String.Format(CultureInfo.CurrentCulture, "Data Source cannot be empty.  Use {0} to open an in-memory database", MemoryFileName));
          else
            fullUri = true;
        }
        else
          fileName = MapUriPath(fileName);
      }

      bool isMemory = (String.Compare(fileName, MemoryFileName, StringComparison.OrdinalIgnoreCase) == 0);

      if (!fullUri)
      {
        if (isMemory)
          fileName = MemoryFileName;
        else
        {
#if PLATFORM_COMPACTFRAMEWORK
          if (fileName.StartsWith("./") || fileName.StartsWith(".\\"))
            fileName = Path.GetDirectoryName(System.Reflection.Assembly.GetCallingAssembly().GetName().CodeBase) + fileName.Substring(1);
#endif
          bool toFullPath = SQLiteConvert.ToBoolean(FindKey(opts, "ToFullPath", DefaultToFullPath.ToString()));
          fileName = ExpandFileName(fileName, toFullPath);
        }
      }

      try
      {
        bool usePooling = SQLiteConvert.ToBoolean(FindKey(opts, "Pooling", DefaultPooling.ToString()));
        int maxPoolSize = Convert.ToInt32(FindKey(opts, "Max Pool Size", DefaultMaxPoolSize.ToString()), CultureInfo.InvariantCulture);

        _defaultTimeout = Convert.ToInt32(FindKey(opts, "Default Timeout", DefaultConnectionTimeout.ToString()), CultureInfo.InvariantCulture);

        enumValue = TryParseEnum(typeof(IsolationLevel), FindKey(opts, "Default IsolationLevel", DefaultIsolationLevel.ToString()), true);
        _defaultIsolation = (enumValue is IsolationLevel) ? (IsolationLevel)enumValue : DefaultIsolationLevel;

        if (_defaultIsolation != IsolationLevel.Serializable && _defaultIsolation != IsolationLevel.ReadCommitted)
          throw new NotSupportedException("Invalid Default IsolationLevel specified");

        _baseSchemaName = FindKey(opts, "BaseSchemaName", DefaultBaseSchemaName);

        if (_sql == null)
        {
            SetupSQLiteBase(opts);
        }

        SQLiteOpenFlagsEnum flags = SQLiteOpenFlagsEnum.None;

        if (!SQLiteConvert.ToBoolean(FindKey(opts, "FailIfMissing", DefaultFailIfMissing.ToString())))
          flags |= SQLiteOpenFlagsEnum.Create;

        if (SQLiteConvert.ToBoolean(FindKey(opts, "Read Only", DefaultReadOnly.ToString())))
        {
          flags |= SQLiteOpenFlagsEnum.ReadOnly;
          // SQLite will return SQLITE_MISUSE on ReadOnly and Create
          flags &= ~SQLiteOpenFlagsEnum.Create;
        }
        else
        {
          flags |= SQLiteOpenFlagsEnum.ReadWrite;
//.........这里部分代码省略.........

 internal abstract int Bind_ParamIndex(SQLiteStatement stmt, SQLiteConnectionFlags flags, string paramName);

 internal abstract int Bind_ParamCount(SQLiteStatement stmt, SQLiteConnectionFlags flags);

 /// <summary>
 /// This function binds a user-defined functions to the connection.
 /// </summary>
 /// <param name="functionAttribute">
 /// The <see cref="SQLiteFunctionAttribute"/> object instance containing
 /// the metadata for the function to be bound.
 /// </param>
 /// <param name="function">
 /// The <see cref="SQLiteFunction"/> object instance that implements the
 /// function to be bound.
 /// </param>
 /// <param name="flags">
 /// The flags associated with the parent connection object.
 /// </param>
 internal abstract void BindFunction(SQLiteFunctionAttribute functionAttribute, SQLiteFunction function, SQLiteConnectionFlags flags);

    /// <summary>
    /// This function binds a user-defined functions to a connection.
    /// </summary>
    /// <param name="sqliteBase">
    /// The <see cref="SQLiteBase" /> object instance associated with the
    /// <see cref="SQLiteConnection" /> that the function should be bound to.
    /// </param>
    /// <param name="functionAttribute">
    /// The <see cref="SQLiteFunctionAttribute"/> object instance containing
    /// the metadata for the function to be bound.
    /// </param>
    /// <param name="function">
    /// The <see cref="SQLiteFunction"/> object instance that implements the
    /// function to be bound.
    /// </param>
    /// <param name="flags">
    /// The flags associated with the parent connection object.
    /// </param>
    internal static void BindFunction(
        SQLiteBase sqliteBase,
        SQLiteFunctionAttribute functionAttribute,
        SQLiteFunction function,
        SQLiteConnectionFlags flags
        )
    {
        if (sqliteBase == null)
            throw new ArgumentNullException("sqliteBase");

        if (functionAttribute == null)
            throw new ArgumentNullException("functionAttribute");

        if (function == null)
            throw new ArgumentNullException("function");

        FunctionType functionType = functionAttribute.FuncType;

        function._base = sqliteBase;
        function._flags = flags;

        function._InvokeFunc = (functionType == FunctionType.Scalar) ?
            new SQLiteCallback(function.ScalarCallback) : null;

        function._StepFunc = (functionType == FunctionType.Aggregate) ?
            new SQLiteCallback(function.StepCallback) : null;

        function._FinalFunc = (functionType == FunctionType.Aggregate) ?
            new SQLiteFinalCallback(function.FinalCallback) : null;

        function._CompareFunc = (functionType == FunctionType.Collation) ?
            new SQLiteCollation(function.CompareCallback) : null;

        function._CompareFunc16 = (functionType == FunctionType.Collation) ?
            new SQLiteCollation(function.CompareCallback16) : null;

        string name = functionAttribute.Name;

        if (functionType != FunctionType.Collation)
        {
            bool needCollSeq = (function is SQLiteFunctionEx);

            sqliteBase.CreateFunction(
                name, functionAttribute.Arguments, needCollSeq,
                function._InvokeFunc, function._StepFunc,
                function._FinalFunc);
        }
        else
        {
            sqliteBase.CreateCollation(
                name, function._CompareFunc, function._CompareFunc16);
        }
    }

    /// <summary>
    /// Called by SQLiteBase derived classes, this function binds all user-defined functions to a connection.
    /// It is done this way so that all user-defined functions will access the database using the same encoding scheme
    /// as the connection (UTF-8 or UTF-16).
    /// </summary>
    /// <remarks>
    /// The wrapper functions that interop with SQLite will create a unique cookie value, which internally is a pointer to
    /// all the wrapped callback functions.  The interop function uses it to map CDecl callbacks to StdCall callbacks.
    /// </remarks>
    /// <param name="sqlbase">The base object on which the functions are to bind</param>
    /// <param name="flags">The flags associated with the parent connection object</param>
    /// <returns>Returns a logical list of functions which the connection should retain until it is closed.</returns>
    internal static IEnumerable<SQLiteFunction> BindFunctions(SQLiteBase sqlbase, SQLiteConnectionFlags flags)
    {
        List<SQLiteFunction> lFunctions = new List<SQLiteFunction>();

        foreach (SQLiteFunctionAttribute pr in _registeredFunctions)
        {
            SQLiteFunction f = (SQLiteFunction)Activator.CreateInstance(pr.InstanceType);
            BindFunction(sqlbase, pr, f, flags);
            lFunctions.Add(f);
        }

        return lFunctions;
    }

    internal override void Bind_Text(SQLiteStatement stmt, SQLiteConnectionFlags flags, int index, string value)
    {
        SQLiteStatementHandle handle = stmt._sqlite_stmt;

#if !PLATFORM_COMPACTFRAMEWORK
        if ((flags & SQLiteConnectionFlags.LogBind) == SQLiteConnectionFlags.LogBind)
        {
            LogBind(handle, index, value);
        }
#endif

        SQLiteErrorCode n = UnsafeNativeMethods.sqlite3_bind_text16(handle, index, value, value.Length * 2, (IntPtr)(-1));
        if (n != SQLiteErrorCode.Ok) throw new SQLiteException(n, GetLastError());
    }

    internal override void Bind_DateTime(SQLiteStatement stmt, SQLiteConnectionFlags flags, int index, DateTime dt)
    {
        switch (_datetimeFormat)
        {
            case SQLiteDateFormats.Ticks:
            case SQLiteDateFormats.JulianDay:
            case SQLiteDateFormats.UnixEpoch:
                {
                    base.Bind_DateTime(stmt, flags, index, dt);
                    break;
                }
            default:
                {
#if !PLATFORM_COMPACTFRAMEWORK
                    if ((flags & SQLiteConnectionFlags.LogBind) == SQLiteConnectionFlags.LogBind)
                    {
                        SQLiteStatementHandle handle =
                            (stmt != null) ? stmt._sqlite_stmt : null;

                        LogBind(handle, index, dt);
                    }
#endif

                    Bind_Text(stmt, flags, index, ToString(dt));
                    break;
                }
        }
    }

    internal override void Open(string strFilename, string vfsName, SQLiteConnectionFlags connectionFlags, SQLiteOpenFlagsEnum openFlags, int maxPoolSize, bool usePool)
    {
      //
      // NOTE: If the database connection is currently open, attempt to
      //       close it now.  This must be done because the file name or
      //       other parameters that may impact the underlying database
      //       connection may have changed.
      //
      if (_sql != null) Close(true);

      //
      // NOTE: If the connection was not closed successfully, throw an
      //       exception now.
      //
      if (_sql != null)
          throw new SQLiteException("connection handle is still active");

      _usePool = usePool;
      _fileName = strFilename;
      _flags = connectionFlags;

      if (usePool)
      {
        _sql = SQLiteConnectionPool.Remove(strFilename, maxPoolSize, out _poolVersion);

        SQLiteConnection.OnChanged(null, new ConnectionEventArgs(
            SQLiteConnectionEventType.OpenedFromPool, null, null,
            null, null, _sql, strFilename, new object[] {
            typeof(SQLite3_UTF16), strFilename, vfsName,
            connectionFlags, openFlags, maxPoolSize, usePool,
            _poolVersion }));

#if !NET_COMPACT_20 && TRACE_CONNECTION
        Trace.WriteLine(UnsafeNativeMethods.StringFormat(
            CultureInfo.CurrentCulture,
            "Open16 (Pool): {0}",
            HandleToString()));
#endif
      }

      if (_sql == null)
      {
        try
        {
            // do nothing.
        }
        finally /* NOTE: Thread.Abort() protection. */
        {
          IntPtr db = IntPtr.Zero;
          SQLiteErrorCode n;

          int extFuncs = ((connectionFlags & SQLiteConnectionFlags.NoExtensionFunctions) != SQLiteConnectionFlags.NoExtensionFunctions) ? 1 : 0;

#if !SQLITE_STANDARD
          if ((vfsName != null) || (extFuncs != 0))
          {
            n = UnsafeNativeMethods.sqlite3_open16_interop(ToUTF8(strFilename), ToUTF8(vfsName), openFlags, extFuncs, ref db);
          }
          else
#endif
          {
            //
            // NOTE: This flag check is designed to enforce the constraint that opening
            //       a database file that does not already exist requires specifying the
            //       "Create" flag, even when a native API is used that does not accept
            //       a flags parameter.
            //
            if (((openFlags & SQLiteOpenFlagsEnum.Create) != SQLiteOpenFlagsEnum.Create) && !File.Exists(strFilename))
              throw new SQLiteException(SQLiteErrorCode.CantOpen, strFilename);

            if (vfsName != null)
            {
              throw new SQLiteException(SQLiteErrorCode.CantOpen, UnsafeNativeMethods.StringFormat(
                CultureInfo.CurrentCulture,
                "cannot open using UTF-16 and VFS \"{0}\": need interop assembly", vfsName));
            }

            n = UnsafeNativeMethods.sqlite3_open16(strFilename, ref db);
          }

#if !NET_COMPACT_20 && TRACE_CONNECTION
          Trace.WriteLine(UnsafeNativeMethods.StringFormat(
              CultureInfo.CurrentCulture,
              "Open16: {0}", db));
#endif

          if (n != SQLiteErrorCode.Ok) throw new SQLiteException(n, null);
          _sql = new SQLiteConnectionHandle(db, true);
        }
        lock (_sql) { /* HACK: Force the SyncBlock to be "created" now. */ }

        SQLiteConnection.OnChanged(null, new ConnectionEventArgs(
            SQLiteConnectionEventType.NewCriticalHandle, null,
            null, null, null, _sql, strFilename, new object[] {
            typeof(SQLite3_UTF16), strFilename, vfsName,
            connectionFlags, openFlags, maxPoolSize, usePool }));
      }

      // Bind functions to this connection.  If any previous functions of the same name
      // were already bound, then the new bindings replace the old.
//.........这里部分代码省略.........

    internal override int Bind_ParamIndex(SQLiteStatement stmt, SQLiteConnectionFlags flags, string paramName)
    {
        SQLiteStatementHandle handle = stmt._sqlite_stmt;
        int index = UnsafeNativeMethods.sqlite3_bind_parameter_index(handle, ToUTF8(paramName));

#if !PLATFORM_COMPACTFRAMEWORK
        if ((flags & SQLiteConnectionFlags.LogBind) == SQLiteConnectionFlags.LogBind)
        {
            //IntPtr handleIntPtr = handle;

            //SQLiteLog.LogMessage(0, String.Format(
            //    "Statement {0} paramter index of name {{{1}}} is #{2}.",
            //    handleIntPtr, paramName, index));
        }
#endif

        return index;
    }

 internal abstract void Bind_DateTime(SQLiteStatement stmt, SQLiteConnectionFlags flags, int index, DateTime dt);

 internal abstract void Bind_Null(SQLiteStatement stmt, SQLiteConnectionFlags flags, int index);

 /// <summary>
 /// Calls the native SQLite core library in order to cleanup the resources
 /// associated with a module containing the implementation of a virtual table.
 /// </summary>
 /// <param name="module">
 /// The module object previously passed to the <see cref="CreateModule" />
 /// method.
 /// </param>
 /// <param name="flags">
 /// The flags for the associated <see cref="SQLiteConnection" /> object instance.
 /// </param>
 internal abstract void DisposeModule(SQLiteModule module, SQLiteConnectionFlags flags);

 internal abstract string Bind_ParamName(SQLiteStatement stmt, SQLiteConnectionFlags flags, int index);

 internal abstract object GetValue(SQLiteStatement stmt, SQLiteConnectionFlags flags, int index, SQLiteType typ);