0perator 0perator -4 years ago 151
C# Question

Refreshing a UI to reflect items added to a list

While my UI is displayed, data is being passed in the back end and added to a

that I would in turn like to display on my UI.

I've seen several examples using background workers however I don't have access to the actual component due to how I layout my User Controls and programmatically build them.

Question: How can I run this method repeatedly behind my UI without locking up my UI in a loop?

public void UpdatePanel()
foreach (var item in list)

Answer Source

Instead of using a loop or time intervals to monitor a list, as an option when possible, you can use a BindingList<T> or ObservableCollection<T> and receive notification when list changes.

Then you can update user interface in the event handler which you attaced to ListChanged event ofBindingList<T> or CollectionChanged event of ObservableCOllection<T>.


Here is an example based on ObservableCollection<string>.

ObservableCollection<string> list;
private void Form1_Load(object sender, EventArgs e)
    list = new ObservableCollection<string>();
    list.CollectionChanged += list_CollectionChanged;
    list.Add("Item 1");
    list.Add("Item 2");
    list[0] = "New Item";
void list_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    if (e.Action == NotifyCollectionChangedAction.Add)
        var items = string.Join(",", e.NewItems.Cast<String>());
        MessageBox.Show(string.Format("'{0}' Added", items));
    else if (e.Action == NotifyCollectionChangedAction.Remove)
        var items = string.Join(",", e.OldItems.Cast<String>());
        MessageBox.Show(string.Format("'{0}' Removed", items));
    else if (e.Action == NotifyCollectionChangedAction.Replace)
        var oldItems = string.Join(",", e.OldItems.Cast<String>());
        var newItems = string.Join(",", e.NewItems.Cast<String>());
        MessageBox.Show(string.Format("'{0}' replaced by '{1}'", oldItems, newItems));
        MessageBox.Show("Reset or Move");
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