I'm trying to add only items that are new to the ObservableCollection, so as not to create duplicates. Everything is in an infinite loop so I can add the new ones. The problem is that I can't figure out the best way to prevent duplicates in the list. To prevent the program from throwing me an exception for comparing items in an empty sheet. So I add them first and if they don't meet the condition, I remove them. But then it flashes on the screen, e.g. in a table, as new items are added. So what to do? Thanks for any suggestions

 bool help = true;
           
            do
            {

                using (var client = new ImapClient())
                {
                    using (var cancel = new CancellationTokenSource())
                    {

                   
                        client.Connect(emailParser.ServerName, emailParser.Port, emailParser.isSSLuse,
                            cancel.Token);
                       
                        //client.AuthenticationMechanisms.Remove("XOAUTH");

                        client.Authenticate(emailParser.Username, emailParser.Password, cancel.Token);

                       
                        var inbox = client.Inbox;
                        inbox.Open(FolderAccess.ReadOnly, cancel.Token);

                        Console.WriteLine("Total messages: {0}", inbox.Count);
                        Console.WriteLine("Recent messages: {0}", inbox.Unread);
                        

                      
                        for (int i = 0; i < inbox.Count; i  )
                        {
                            var message = inbox.GetMessage(i, cancel.Token);

                                alerts.Add(message); // I Think the problem is here

                            for (int j = 0; j < alerts.Count-1; j  )
                            {
                                if (alerts[j].MessageId.Equals(message.MessageId))
                                {
                                    alerts.Remove(message);
                                }
                            }
                        
                        }
                        Console.WriteLine(alerts.Count);
                        alerts.Count();
                    
                    }
                    client.Disconnect(true);
                    
                }
          
        } while (help != false);

CodePudding user response：

Use LINQ's Any method for enumerables which is safe against empty collections

CodePudding user response：

How about you not add the item unless the condition is met, instead of adding and removing later? If you do, your for loop becomes

for (int i = 0; i < inbox.Count; i  )
{
    var message = inbox.GetMessage(i, cancel.Token);
    if (!alerts.Any(x => x.MessageId.Equals(message.MessageId))
    {
        alerts.Add(message);
    }
}