how to update my notification?

i made an application that allow me to open conversation between friends, when someone send me a message i got a notification "John send you a new message" and when another person in the conversation send me a message a new notification is made ,,, my problem is that i don't want to make a new notification but i want to update the old notification to be for ex. like this " John and Alfred send you a new message"..

        var user = users.Where(x => x != CurrentUserId);

        foreach (var item in user)
        {
            var check = entities.Notifications.SingleOrDefault(i => (i.NotificationForId == id
                                      && i.NotificationForType == IdType && i.UserId == item));
            if (check == null)
            {
                Notification notify = new Notification()
                {
                    NotificationForId = id,
                    NotificationForType = IdType,
                    DateTime = DateTime.Now,
                    Message = GenerateMessage(),
                    UserId = item,
                    SenderID = CurrentUserId.ToString(),
                    Sende开发者_开发知识库rName = CurrentUserName
                };

                entities.Notifications.AddObject(notify);
            }
            else
            {

                check.Checked = false;
                check.DateTime = DateTime.Now;
            }

here it check if there are any notification for a user , if null then make a new notification else " Update the notification "

Your else block indicates the notification exists on the database, you can update the properties there. To save the changes made, both for insert and update call the method entities.SaveChanges()