//******************************************************************************************************//  DataSourceLookups.cs - Gbtc////  Copyright © 2016, Grid Protection Alliance.  All Rights Reserved.////  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See//  the NOTICE file distributed with this work for additional information regarding copyright ownership.//  The GPA licenses this file to you under the MIT License (MIT), the "License"; you may//  not use this file except in compliance with the License. You may obtain a copy of the License at:////      http://www.opensource.org/licenses/MIT////  Unless agreed to in writing, the subject software distributed under the License is distributed on an//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the//  License for the specific language governing permissions and limitations.////  Code Modification History://  ----------------------------------------------------------------------------------------------------//  10/31/2016 - Steven E. Chisholm//       Generated original version of source code.////****************************************************************************************************** using System;using System.Collections.Generic;using System.Data;using GSF.Diagnostics; namespace GSF.TimeSeries.Data{    /// <summary>    /// Creates a cached lookup so certain metadata so lookups can occur with quickly.    /// </summary>    public static class DataSourceLookups    {        private static readonly LogPublisher s_log = Logger.CreatePublisher(typeof(DataSourceLookups), MessageClass.Framework);         private static readonly List<WeakReference<DataSourceLookupCache>> s_dataSetLookups = new List<WeakReference<DataSourceLookupCache>>();         /// <summary>        /// Gets/Creates the lookup cache for the provided dataset.        /// </summary>        /// <param name="dataSet">The non-null dataset provided by the time-series framework</param>        /// <returns>Lookup cache for the provided dataset.</returns>        public static DataSourceLookupCache GetLookupCache(DataSet dataSet)        {            if ((object)dataSet == null)                throw new ArgumentNullException(nameof(dataSet));             //Since adding datasets will be rare, the penalty associated with a lock on the entire            //set will be minor.            lock (s_dataSetLookups)            {                DataSourceLookupCache target;                 for (int index = 0; index < s_dataSetLookups.Count; index++)                {                    WeakReference<DataSourceLookupCache> item = s_dataSetLookups[index];                     if (item.TryGetTarget(out target) && target.DataSet != null)                    {                        if (ReferenceEquals(target.DataSet, dataSet))                        {                            return target;                        }                    }                    else                    {                        s_log.Publish(MessageLevel.Info, "A DataSet object has been disposed or garbage collected. It will be removed from the list.");                        s_dataSetLookups.RemoveAt(index);                        index--;                    }                }                 s_log.Publish(MessageLevel.Info, "Creating a lookup cache for a dataset");                target = new DataSourceLookupCache(dataSet);                 s_dataSetLookups.Add(new WeakReference<DataSourceLookupCache>(target));                 return target;            }        }         /// <summary>        /// Gets/Creates the <see cref="ActiveMeasurementsTableLookup"/> for the provided dataset.        /// </summary>        /// <param name="dataSet"></param>        /// <returns><see cref="ActiveMeasurementsTableLookup"/> for the provided dataset.</returns>        public static ActiveMeasurementsTableLookup ActiveMeasurements(DataSet dataSet)        {            return GetLookupCache(dataSet).ActiveMeasurements;        }    }}