OcExt.cs

public static class OcExt
{
    public static void InvokeAdd<T>(this ObservableCollection<T> collection, T newItem)
    {
        collection.Invoke(()=>collection.Add(newItem));
    }
    public static void InvokeAddRange<T>(this ObservableCollection<T> collection, IEnumerable<T> newItems)
    {
        collection.Invoke(() =>
        {
            foreach (var newItem in newItems)
            {
                collection.Add(newItem);
            }
        });
    }
    public static void InvokeRemove<T>(this ObservableCollection<T> collection, T oldItem)
    {
        collection.Invoke(() => collection.Remove(oldItem));
    }
    public static void InvokeClear<T>(this ObservableCollection<T> collection)
    {
        collection.Invoke(() => collection.Clear());
    }
    public static void Invoke<T>(this ObservableCollection<T> col, Action action)
    {
        Dispatcher dispatcher = Application.Current != null
            ? Application.Current.Dispatcher
            : Dispatcher.CurrentDispatcher;
        dispatcher.Invoke(action);
    }
    public static DispatcherOperation AddAsync<T>(this ObservableCollection<T> collection, T newItem)
    {
        return collection.InvokeAsync(() => collection.Add(newItem));
    }
    public static DispatcherOperation AddRangeAsync<T>(this ObservableCollection<T> collection, IEnumerable<T> newItems)
    {
        return collection.InvokeAsync(() =>
        {
            foreach (var newItem in newItems)
            {
                collection.Add(newItem);
            }
        });
    }
    public static DispatcherOperation RemoveAsync<T>(this ObservableCollection<T> collection, T oldItem)
    {
        return collection.InvokeAsync(() => collection.Remove(oldItem));
    }
    public static DispatcherOperation ClearAsync<T>(this ObservableCollection<T> collection)
    {
        return collection.InvokeAsync(() => collection.Clear());
    }
    public static DispatcherOperation InvokeAsync<T>(this ObservableCollection<T> col, Action action)
    {
        Dispatcher dispatcher = Application.Current != null
            ? Application.Current.Dispatcher
            : Dispatcher.CurrentDispatcher;
        return dispatcher.InvokeAsync(action);
    }
}