Additional check if child session has already been closed.

[itmagination]

This simple fix prevents unnecessary SessionException("Session was already closed") throw when both parent session and child session are closed separately (order does not matter). Before invoking close on child session (during parent session close) we should check if child session has not been closed already. Unfortunately to check if session was closed we have to use SessionImpl class instead of ISession interface, so we changed SessionImpl’s childSessionsByEntityMode private field type IDictionary<EntityMode, ISession> into IDictionary<EntityMode, SessionImpl>.

[hazzik]

Please use ISessionImplementor instead of SessionImpl

[itmagination]

I used ISessionImplementor instead of SessionImpl as requested. Unfortunately I had to add Close method in ISessionImplementor interface and make other necessary changes in dependent types (add abstract Close method in AbstractSessionImpl etc.). In GetSession method of SessionImpl class I had to cast result to ISession interface, because there is no formal connection between ISession and ISessionImplementator interfaces.

[hazzik]

Hi @itmagination.

There is ISession.IsOpen property which implementation is exactly !IsClosed, so, this change shall be only one line:

if (pair.Value.IsOpen)
{
     pair.Value.Close();
}

No other changes are required.

[itmagination]

Oh my! You're right! I've closed this knotty PR and opened a new one #542 containing this simple fix. Thank you!