I’m trying to dynamically add new records to DataGrid. I’m using HashSet to prevent duplicates. But when I want to add objects from HashSet to ObservableCollection, I get the error:

Cannot apply indexing with [] to an expression of type
‘system.collections.generic.ienumerable<>.

I have implemented IEnumarable.

Contructor in AdminWindow.xaml.cs class

 public AdminWindow()
        {
            InitializeComponent();
            ObservableCollection<Alert> alertToDataGrid = new ObservableCollection<Alert>();
           
            for (int i = 0; i < Alert.alerts.Count; i++)
            {
                alertToDataGrid.Add(Alert.alerts[i]); //Here is the issue
            }

            AlertTable.ItemsSource = alertToDataGrid;
        }

Alert Class

public class Alert:IEnumerable<Alert>
        {
            private string id;
            private DateTime date;
            private string email;
            private string nameOfAlert;
            private string typeOfAlert; // will be enum later
            public static HashSet<Alert> alerts = new HashSet<Alert>();
    
            public override string ToString()
            {
                return id + "\n" + Date+  "\n" + email + "\n" + nameOfAlert + "\n" + typeOfAlert;
            }
    
            public override bool Equals(object obj)
            {
                return obj is Alert alert &&
                       id == alert.id &&
                       Id == alert.Id;
            }
    
            public override int GetHashCode()
            {
                return HashCode.Combine(id, Id);
            }
            //Tried just to return Enumerator
            public IEnumerator<Alert> GetEnumerator()
            {
                foreach (Alert alert in alerts)
                {
                    yield return alert;
                }
            }
    
            IEnumerator IEnumerable.GetEnumerator()
            {
                return this.GetEnumerator();
            }
    
            public Alert(string id, DateTime date , string email, string nameOfAlert, string typeOfAlert)
            {
                this.Id = id;
                this.Date = date;
                this.Email = email;
                this.NameOfAlert = nameOfAlert;
                this.TypeOfAlert = typeOfAlert;
            }
    
            public string Id { get => id; set => id = value; }
            public string Email { get => email; set => email = value; }
            public string NameOfAlert { get => nameOfAlert; set => nameOfAlert = value; }
            public string TypeOfAlert { get => typeOfAlert; set => typeOfAlert = value; }
            public DateTime Date { get => date; set => date = value; }
        }

>Solution :

You could also try

foreach (Alert alert in Alert.alerts) {
  alertToDataGrid.Add(alert);
}

See How can I enumerate through a HashSet? for more details