我想做的是FreezableCollection.AddRange（collectionToAdd） [英] What I want to do is FreezableCollection.AddRange(collectionToAdd)

问题描述

我想要做的是 FreezableCollection.AddRange（collectionToAdd）

每次我添加到FreezableCollection一个事件被提出，一些事情发生。现在我有一个新的集合，我想添加，但这一次我想让FreezableCollection的 CollectionChanged事件只触发一次。

循环通过和添加它们将为每个新项目引发事件。

有一种方法，我可以添加到FreezableCollection的目标，类似List.AddRange？ p>

解决方案

从集合中导出并覆盖您要更改的行为。我可以这样做：

  public class PrestoObservableCollection< T> ：ObservableCollection< T> 
 {
 private bool _delayOnCollectionChangedNotification {get;组; } 
 
 ///< sum> 
 ///向可观察集合中添加一系列IEnumerable项，并且可选地延迟通知，直到操作完成。 
 ///< / summary> 
 ///< param name =itemsToAdd>< / param> 
 public void AddRange（IEnumerable< T> itemsToAdd）
 {
 if（itemsToAdd == null）throw new ArgumentNullException（itemsToAdd）; 
 
 if（itemsToAdd.Any（）== false）{return; } //无法添加。 
 
 _delayOnCollectionChangedNotification = true; 
 
 try 
 {
 foreach（itemsToAdd中的T项）{this.Add（item）; } 
} 
 finally 
 {
 ResetNotificationAndFireChangedEvent（）; 
} 
} 
 
 ///< summary> 
 ///清除ObservableCollection中的项目，并且可选地延迟通知，直到操作完成。 
 ///< / summary> 
 public void ClearItemsAndNotifyChangeOnlyWhenDone（）
 {
 try 
 {
 if（！this.Any（））{return; } //没有可用的删除。 
 
 _delayOnCollectionChangedNotification = true; 
 
 this.Clear（）; 
} 
 finally 
 {
 ResetNotificationAndFireChangedEvent（）; 
} 
} 
 
 ///< summary> 
 ///覆盖ObservableCollection类上的虚拟OnCollectionChanged（）方法。 
 ///< / summary> 
 ///< param name =e>事件参数< / param> 
 protected override void OnCollectionChanged（NotifyCollectionChangedEventArgs e）
 {
 if（_delayOnCollectionChangedNotification）{return; } 
 
 base.OnCollectionChanged（e）; 
} 
 
 private void ResetNotificationAndFireChangedEvent（）
 {
 //关闭延迟通知并调用OnCollectionChanged（）方法，并告诉我们集合中有变化。 
 _delayOnCollectionChangedNotification = false; 
 this.OnCollectionChanged（new NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Reset））; 
} 
} 
  

What I want to do is FreezableCollection.AddRange(collectionToAdd)

Each time I add to the FreezableCollection an event is raised and something happens. Now I have a new collection I would want to add but this time I want the CollectionChanged event of the FreezableCollection to fire only once.

Looping through and adding them will raise the event for each new item.

Is there a way I can add to FreezableCollection all at a goal, similar to List.AddRange?

解决方案

Derive from a collection and override the behavior that you'd like to change. I was able to do it this way:

public class PrestoObservableCollection<T> : ObservableCollection<T>
    {
        private bool _delayOnCollectionChangedNotification { get; set; }

        /// <summary>
        /// Add a range of IEnumerable items to the observable collection and optionally delay notification until the operation is complete.
        /// </summary>
        /// <param name="itemsToAdd"></param>
        public void AddRange(IEnumerable<T> itemsToAdd)
        {
            if (itemsToAdd == null) throw new ArgumentNullException("itemsToAdd");

            if (itemsToAdd.Any() == false) { return; }  // Nothing to add.

            _delayOnCollectionChangedNotification = true;            

            try
            {
                foreach (T item in itemsToAdd) { this.Add(item); }
            }
            finally
            {
                ResetNotificationAndFireChangedEvent();
            }
        }

        /// <summary>
        /// Clear the items in the ObservableCollection and optionally delay notification until the operation is complete.
        /// </summary>
        public void ClearItemsAndNotifyChangeOnlyWhenDone()
        {
            try
            {
                if (!this.Any()) { return; }  // Nothing available to remove.

                _delayOnCollectionChangedNotification = true;

                this.Clear();
            }
            finally
            {
                ResetNotificationAndFireChangedEvent();
            }
        }

        /// <summary>
        /// Override the virtual OnCollectionChanged() method on the ObservableCollection class.
        /// </summary>
        /// <param name="e">Event arguments</param>
        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if (_delayOnCollectionChangedNotification) { return; }

            base.OnCollectionChanged(e);
        }

        private void ResetNotificationAndFireChangedEvent()
        {
            // Turn delay notification off and call the OnCollectionChanged() method and tell it we had a change in the collection.
            _delayOnCollectionChangedNotification = false;
            this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
        }
    }

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