NH-3897 - Makes DebugConnectionProvider.connections thread safe. (#495)

Fixes NH-3436 failing for me when multiple threads try to extend
the HashSet at the same time.

Author: ngbrown

src/NHibernate.Test/DebugConnectionProvider.cs

@@ -1,7 +1,7 @@
 using System;
-using System.Collections;
-using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Data;
+using System.Linq;
 using NHibernate.Connection;
 
 namespace NHibernate.Test
@@ -12,70 +12,49 @@ namespace NHibernate.Test
 	/// </summary>
 	public class DebugConnectionProvider : DriverConnectionProvider
 	{
-		private ISet<IDbConnection> connections = new HashSet<IDbConnection>();
+		private ConcurrentDictionary<IDbConnection, byte> connections = new ConcurrentDictionary<IDbConnection, byte>();
 
 		public override IDbConnection GetConnection()
 		{
 			try
 			{
 				IDbConnection connection = base.GetConnection();
-				connections.Add(connection);
+				connections.TryAdd(connection, 0);
 				return connection;
 			}
 			catch (Exception e)
 			{
 				throw new HibernateException("Could not open connection to: " + ConnectionString, e);
 			}
-
 		}
 
 		public override void CloseConnection(IDbConnection conn)
 		{
 			base.CloseConnection(conn);
-			connections.Remove(conn);
+			byte _;
+			connections.TryRemove(conn, out _);
 		}
 
 		public bool HasOpenConnections
 		{
 			get
 			{
-				// check to see if all connections that were at one point opened
-				// have been closed through the CloseConnection
-				// method
-				if (connections.Count == 0)
-				{
-					// there are no connections, either none were opened or
-					// all of the closings went through CloseConnection.
-					return false;
-				}
-				else
-				{
-					// Disposing of an ISession does not call CloseConnection (should it???)
-					// so a Diposed of ISession will leave an IDbConnection in the list but
-					// the IDbConnection will be closed (atleast with MsSql it works this way).
-					foreach (IDbConnection conn in connections)
-					{
-						if (conn.State != ConnectionState.Closed)
-						{
-							return true;
-						}
-					}
-
-					// all of the connections have been Disposed and were closed that way
-					// or they were Closed through the CloseConnection method.
-					return false;
-				}
+				// Disposing of an ISession does not call CloseConnection (should it???)
+				// so a Diposed of ISession will leave an IDbConnection in the list but
+				// the IDbConnection will be closed (atleast with MsSql it works this way).
+				return connections.Keys.Any(conn => conn.State != ConnectionState.Closed);
 			}
 		}
 
 		public void CloseAllConnections()
 		{
 			while (connections.Count != 0)
 			{
-				IEnumerator en = connections.GetEnumerator();
-				en.MoveNext();
-				CloseConnection(en.Current as IDbConnection);
+				foreach (var conn in connections.Keys.ToArray())
+				{
+					CloseConnection(conn);
+				}
 			}
 		}
 	}
-}
+}