Additional check if child session has already been closed.

src/NHibernate/Engine/ISessionImplementor.cs

@@ -306,7 +306,12 @@ public interface ISessionImplementor
 		/// </returns>
 		bool IsClosed { get; }
 
-		void Flush();
+        /// <summary>
+        /// Close the session and release all resources.
+        /// </summary>
+        IDbConnection Close();
+
+        void Flush();
 
 		/// <summary> 
 		/// Does this <tt>Session</tt> have an active Hibernate transaction

src/NHibernate/IStatelessSession.cs

@@ -60,7 +60,7 @@ public interface IStatelessSession : IDisposable
 		ISessionImplementor GetSessionImplementation();
 
 		/// <summary>Close the stateless session and release the ADO.NET connection.</summary>
-		void Close();
+		IDbConnection Close();
 
 		/// <summary>Insert an entity.</summary>
 		/// <param name="entity">A new transient instance</param>

src/NHibernate/Impl/AbstractSessionImpl.cs

@@ -298,7 +298,9 @@ public bool IsClosed
 			get { return closed; }
 		}
 
-		protected internal virtual void CheckAndUpdateSessionStatus()
+	    public abstract IDbConnection Close();
+
+	    protected internal virtual void CheckAndUpdateSessionStatus()
 		{
 			ErrorIfClosed();
 			EnlistInAmbientTransactionIfNeeded();

src/NHibernate/Impl/SessionImpl.cs

@@ -78,7 +78,7 @@ public sealed class SessionImpl : AbstractSessionImpl, IEventSource, ISerializab
 		private readonly ISession rootSession;
 
 		[NonSerialized]
-		private IDictionary<EntityMode, ISession> childSessionsByEntityMode;
+        private IDictionary<EntityMode, ISessionImplementor> childSessionsByEntityMode;
 
 		[NonSerialized]
 		private readonly bool flushBeforeCompletionEnabled;
@@ -351,7 +351,7 @@ public bool ShouldAutoClose
 		/// Close() is not aware of distributed transactions
 		/// </remarks>
 		/// </summary>
-		public IDbConnection Close()
+		public override IDbConnection Close()
 		{
 			using (new SessionIdLoggingContext(SessionId))
 			{
@@ -372,9 +372,12 @@ public IDbConnection Close()
 					{
 						if (childSessionsByEntityMode != null)
 						{
-							foreach (KeyValuePair<EntityMode, ISession> pair in childSessionsByEntityMode)
+							foreach (KeyValuePair<EntityMode, ISessionImplementor> pair in childSessionsByEntityMode)
 							{
-								pair.Value.Close();
+							    if (!pair.Value.IsClosed)
+							    {
+								    pair.Value.Close();
+							    }
 							}
 						}
 					}
@@ -2243,10 +2246,10 @@ public ISession GetSession(EntityMode entityMode)
 
 				CheckAndUpdateSessionStatus();
 
-				ISession rtn = null;
+                ISessionImplementor rtn = null;
 				if (childSessionsByEntityMode == null)
 				{
-					childSessionsByEntityMode = new Dictionary<EntityMode, ISession>();
+                    childSessionsByEntityMode = new Dictionary<EntityMode, ISessionImplementor>();
 				}
 				else
 				{
@@ -2260,7 +2263,7 @@ public ISession GetSession(EntityMode entityMode)
 					childSessionsByEntityMode.Add(entityMode, rtn);
 				}
 
-				return rtn;
+				return (ISession)rtn;
 			}
 		}
 

src/NHibernate/Impl/StatelessSessionImpl.cs

@@ -439,24 +439,25 @@ public ISessionImplementor GetSessionImplementation()
 		}
 
 		/// <summary> Close the stateless session and release the ADO.NET connection.</summary>
-		public void Close()
+		public override IDbConnection Close()
 		{
 			using (new SessionIdLoggingContext(SessionId))
 			{
-				ManagedClose();
+				return ManagedClose();
 			}
 		}
 
-		public void ManagedClose()
+		public IDbConnection ManagedClose()
 		{
 			using (new SessionIdLoggingContext(SessionId))
 			{
 				if (IsClosed)
 				{
 					throw new SessionException("Session was already closed!");
 				}
-				ConnectionManager.Close();
+				var dbConection = ConnectionManager.Close();
 				SetClosed();
+			    return dbConection;
 			}
 		}