Avalonia/tests/Perspex.Base.UnitTests/Collections/CollectionChangedTracker.cs

// -----------------------------------------------------------------------
// <copyright file="CollectionChangedTracker.cs" company="Steven Kirk">
// Copyright 2015 MIT Licence. See licence.md for more information.
// </copyright>
// -----------------------------------------------------------------------

namespace Perspex.Base.UnitTests.Collections
{
    using System;
    using System.Collections.Specialized;

    internal class CollectionChangedTracker
    {
        public CollectionChangedTracker(INotifyCollectionChanged collection)
        {
            collection.CollectionChanged += this.CollectionChanged;
        }

        public NotifyCollectionChangedEventArgs Args { get; private set; }

        public void Reset()
        {
            this.Args = null;
        }

        private void CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (this.Args != null)
            {
                throw new Exception("CollectionChanged called more than once.");
            }

            this.Args = e;
        }
    }
}