void OnError(object sender, Exception ex)
{
Trace.Call(sender);
#if LOG4NET
_Logger.Error("OnError(): Exception", ex);
#endif
var builder = CreateMessageBuilder();
builder.AppendEventPrefix();
builder.AppendErrorText(_("Error: {0}"), String.Empty);
builder.AppendMessage(ex.Message);
Session.AddMessageToChat(NetworkChat, builder.ToMessage());
}