How to insert an item at the beginning of an ObservableCollection?

Question

How can I do that? I need a list (of type ObservableCollection) where the latest item is first.

Answer 1

Try using

collection.Insert(0, item);

This would add item to the beginning of the collection (while Add adds to the end). More info here.

Answer 2

You should use a stack instead.

This is based on Observable Stack and Queue

Create an observable Stack, where stack is always last in first out (LIFO).

from Sascha Holl

public class ObservableStack<T> : Stack<T>, INotifyCollectionChanged, INotifyPropertyChanged
{
    public ObservableStack()
    {
    }

    public ObservableStack(IEnumerable<T> collection)
    {
        foreach (var item in collection)
            base.Push(item);
    }

    public ObservableStack(List<T> list)
    {
        foreach (var item in list)
            base.Push(item);
    }


    public new virtual void Clear()
    {
        base.Clear();
        this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }

    public new virtual T Pop()
    {
        var item = base.Pop();
        this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, item));
        return item;
    }

    public new virtual void Push(T item)
    {
        base.Push(item);
        this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item));
    }


    public virtual event NotifyCollectionChangedEventHandler CollectionChanged;


    protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        this.RaiseCollectionChanged(e);
    }

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        this.RaisePropertyChanged(e);
    }


    protected virtual event PropertyChangedEventHandler PropertyChanged;


    private void RaiseCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        if (this.CollectionChanged != null)
            this.CollectionChanged(this, e);
    }

    private void RaisePropertyChanged(PropertyChangedEventArgs e)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, e);
    }


    event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged
    {
        add { this.PropertyChanged += value; }
        remove { this.PropertyChanged -= value; }
    }
}

This calls INotifyCollectionChanged, does the same as a ObservableCollection, but in a stack manner.

Answer 3

you can try this

collection.insert(0,collection.ElementAt(collection.Count - 1));