mono/mcs/class/referencesource/System.Data/System/Data/SqlClient/SqlReferenceCollection.cs

//------------------------------------------------------------------------------
// <copyright file="SqlReferenceCollection.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <owner current="true" primary="true">[....]</owner>
// <owner current="true" primary="false">[....]</owner>
//------------------------------------------------------------------------------

using System;
using System.Data;
using System.Data.Common;
using System.Diagnostics;
using System.Data.ProviderBase;
using System.Threading;
using System.Threading.Tasks;

namespace System.Data.SqlClient {
    sealed internal class SqlReferenceCollection : DbReferenceCollection {
        internal const int DataReaderTag  = 1;
        internal const int CommandTag = 2;
        internal const int BulkCopyTag = 3;

        override public void Add(object value, int tag) {
            Debug.Assert(DataReaderTag == tag || CommandTag == tag || BulkCopyTag == tag, "unexpected tag?");
            Debug.Assert(DataReaderTag != tag || value is SqlDataReader, "tag doesn't match object type: SqlDataReader");
            Debug.Assert(CommandTag != tag || value is SqlCommand, "tag doesn't match object type: SqlCommand");
            Debug.Assert(BulkCopyTag != tag || value is SqlBulkCopy, "tag doesn't match object type: SqlBulkCopy");

            base.AddItem(value, tag);
        }

        internal void Deactivate() {
            base.Notify(0); 
        }

        internal SqlDataReader FindLiveReader(SqlCommand command) {
            if (command == null) {
                // if null == command, will find first live datareader
                return FindItem<SqlDataReader>(DataReaderTag, (dataReader) => (!dataReader.IsClosed));
            }
            else {
                // else will find live datareader assocated with the command
                return FindItem<SqlDataReader>(DataReaderTag, (dataReader) => ((!dataReader.IsClosed) && (command == dataReader.Command)));
            }
        }

        // Finds a SqlCommand associated with the given StateObject
        internal SqlCommand FindLiveCommand(TdsParserStateObject stateObj) {
            return FindItem<SqlCommand>(CommandTag, (command) => (command.StateObject == stateObj));
        }

        override protected void NotifyItem(int message, int tag, object value) {
            Debug.Assert(0 == message, "unexpected message?");
            Debug.Assert(DataReaderTag == tag || CommandTag == tag || BulkCopyTag == tag, "unexpected tag?");
            
            if (tag == DataReaderTag) {
                Debug.Assert(value is SqlDataReader, "Incorrect object type");
                var rdr = (SqlDataReader)value;
                if (!rdr.IsClosed) {
                    rdr.CloseReaderFromConnection();
                }
            }
            else if (tag == CommandTag) {
                Debug.Assert(value is SqlCommand, "Incorrect object type");
                ((SqlCommand)value).OnConnectionClosed();
            }
            else if (tag == BulkCopyTag) {
                Debug.Assert(value is SqlBulkCopy, "Incorrect object type");
                ((SqlBulkCopy)value).OnConnectionClosed();
            }
        }

        override public void Remove(object value) {
            Debug.Assert(value is SqlDataReader || value is SqlCommand || value is SqlBulkCopy, "SqlReferenceCollection.Remove expected a SqlDataReader or SqlCommand or SqlBulkCopy");
            
            base.RemoveItem(value);
        }
    }
}