我希望能够添加一个范围并为整个批量更新。
我还希望能够在操作完成之前取消操作(即除了“更改”之外的集合更改)。
首先,请对 .NET repo上的API 请求进行 投票和评论。
这是我的优化版本ObservableRangeCollection(James Montemagno 的优化版本)。
ObservableRangeCollection
它的执行速度非常快,旨在尽可能重用现有元素并避免不必要的事件,或者尽可能将它们批处理为一个。该ReplaceRange方法通过适当的索引替换/删除/添加所需的元素,并对可能的事件进行批处理。
ReplaceRange
在 Xamarin.Forms UI 上进行了测试,非常频繁地更新大型集合(每秒 5-7 次更新),结果非常好。
注意:由于 WPF 不习惯使用范围操作,所以在 WPF UI 相关的工作中NotSupportedException使用ObservableRangeCollectionfrom below 时会抛出一个 , 例如将其绑定到 aListBox等(您仍然可以使用ObservableRangeCollection<T>if not bound to UI) . 但是,您可以使用WpfObservableRangeCollection<T>解决方法。 真正的解决方案是创建一个CollectionView知道如何处理范围操作的,但我仍然没有时间实现它。
NotSupportedException
ListBox
ObservableRangeCollection<T>
WpfObservableRangeCollection<T>
CollectionView
RAW 代码 - 以 Raw 格式打开,然后按Ctrl+A选择全部,然后Ctrl+C复制。
Ctrl
A
C
// Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. // See the LICENSE file in the project root for more information. using System.Collections.Generic; using System.Collections.Specialized; using System.ComponentModel; using System.Diagnostics; namespace System.Collections.ObjectModel { /// <summary> /// Implementation of a dynamic data collection based on generic Collection<T>, /// implementing INotifyCollectionChanged to notify listeners /// when items get added, removed or the whole list is refreshed. /// </summary> public class ObservableRangeCollection<T> : ObservableCollection<T> { //------------------------------------------------------ // // Private Fields // //------------------------------------------------------ #region Private Fields [NonSerialized] private DeferredEventsCollection _deferredEvents; #endregion Private Fields //------------------------------------------------------ // // Constructors // //------------------------------------------------------ #region Constructors /// <summary> /// Initializes a new instance of ObservableCollection that is empty and has default initial capacity. /// </summary> public ObservableRangeCollection() { } /// <summary> /// Initializes a new instance of the ObservableCollection class that contains /// elements copied from the specified collection and has sufficient capacity /// to accommodate the number of elements copied. /// </summary> /// <param name="collection">The collection whose elements are copied to the new list.</param> /// <remarks> /// The elements are copied onto the ObservableCollection in the /// same order they are read by the enumerator of the collection. /// </remarks> /// <exception cref="ArgumentNullException"> collection is a null reference </exception> public ObservableRangeCollection(IEnumerable<T> collection) : base(collection) { } /// <summary> /// Initializes a new instance of the ObservableCollection class /// that contains elements copied from the specified list /// </summary> /// <param name="list">The list whose elements are copied to the new list.</param> /// <remarks> /// The elements are copied onto the ObservableCollection in the /// same order they are read by the enumerator of the list. /// </remarks> /// <exception cref="ArgumentNullException"> list is a null reference </exception> public ObservableRangeCollection(List<T> list) : base(list) { } #endregion Constructors //------------------------------------------------------ // // Public Methods // //------------------------------------------------------ #region Public Methods /// <summary> /// Adds the elements of the specified collection to the end of the <see cref="ObservableCollection{T}"/>. /// </summary> /// <param name="collection"> /// The collection whose elements should be added to the end of the <see cref="ObservableCollection{T}"/>. /// The collection itself cannot be null, but it can contain elements that are null, if type T is a reference type. /// </param> /// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception> public void AddRange(IEnumerable<T> collection) { InsertRange(Count, collection); } /// <summary> /// Inserts the elements of a collection into the <see cref="ObservableCollection{T}"/> at the specified index. /// </summary> /// <param name="index">The zero-based index at which the new elements should be inserted.</param> /// <param name="collection">The collection whose elements should be inserted into the List<T>. /// The collection itself cannot be null, but it can contain elements that are null, if type T is a reference type.</param> /// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception> /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is not in the collection range.</exception> public void InsertRange(int index, IEnumerable<T> collection) { if (collection == null) throw new ArgumentNullException(nameof(collection)); if (index < 0) throw new ArgumentOutOfRangeException(nameof(index)); if (index > Count) throw new ArgumentOutOfRangeException(nameof(index)); if (collection is ICollection<T> countable) { if (countable.Count == 0) { return; } } else if (!ContainsAny(collection)) { return; } CheckReentrancy(); //expand the following couple of lines when adding more constructors. var target = (List<T>)Items; target.InsertRange(index, collection); OnEssentialPropertiesChanged(); if (!(collection is IList list)) list = new List<T>(collection); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, list, index)); } /// <summary> /// Removes the first occurence of each item in the specified collection from the <see cref="ObservableCollection{T}"/>. /// </summary> /// <param name="collection">The items to remove.</param> /// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception> public void RemoveRange(IEnumerable<T> collection) { if (collection == null) throw new ArgumentNullException(nameof(collection)); if (Count == 0) { return; } else if (collection is ICollection<T> countable) { if (countable.Count == 0) return; else if (countable.Count == 1) using (IEnumerator<T> enumerator = countable.GetEnumerator()) { enumerator.MoveNext(); Remove(enumerator.Current); return; } } else if (!(ContainsAny(collection))) { return; } CheckReentrancy(); var clusters = new Dictionary<int, List<T>>(); var lastIndex = -1; List<T> lastCluster = null; foreach (T item in collection) { var index = IndexOf(item); if (index < 0) { continue; } Items.RemoveAt(index); if (lastIndex == index && lastCluster != null) { lastCluster.Add(item); } else { clusters[lastIndex = index] = lastCluster = new List<T> { item }; } } OnEssentialPropertiesChanged(); if (Count == 0) OnCollectionReset(); else foreach (KeyValuePair<int, List<T>> cluster in clusters) OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, cluster.Value, cluster.Key)); } /// <summary> /// Iterates over the collection and removes all items that satisfy the specified match. /// </summary> /// <remarks>The complexity is O(n).</remarks> /// <param name="match"></param> /// <returns>Returns the number of elements that where </returns> /// <exception cref="ArgumentNullException"><paramref name="match"/> is null.</exception> public int RemoveAll(Predicate<T> match) { return RemoveAll(0, Count, match); } /// <summary> /// Iterates over the specified range within the collection and removes all items that satisfy the specified match. /// </summary> /// <remarks>The complexity is O(n).</remarks> /// <param name="index">The index of where to start performing the search.</param> /// <param name="count">The number of items to iterate on.</param> /// <param name="match"></param> /// <returns>Returns the number of elements that where </returns> /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is out of range.</exception> /// <exception cref="ArgumentOutOfRangeException"><paramref name="count"/> is out of range.</exception> /// <exception cref="ArgumentNullException"><paramref name="match"/> is null.</exception> public int RemoveAll(int index, int count, Predicate<T> match) { if (index < 0) throw new ArgumentOutOfRangeException(nameof(index)); if (count < 0) throw new ArgumentOutOfRangeException(nameof(count)); if (index + count > Count) throw new ArgumentOutOfRangeException(nameof(index)); if (match == null) throw new ArgumentNullException(nameof(match)); if (Count == 0) return 0; List<T> cluster = null; var clusterIndex = -1; var removedCount = 0; using (BlockReentrancy()) using (DeferEvents()) { for (var i = 0; i < count; i++, index++) { T item = Items[index]; if (match(item)) { Items.RemoveAt(index); removedCount++; if (clusterIndex == index) { Debug.Assert(cluster != null); cluster.Add(item); } else { cluster = new List<T> { item }; clusterIndex = index; } index--; } else if (clusterIndex > -1) { OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, cluster, clusterIndex)); clusterIndex = -1; cluster = null; } } if (clusterIndex > -1) OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, cluster, clusterIndex)); } if (removedCount > 0) OnEssentialPropertiesChanged(); return removedCount; } /// <summary> /// Removes a range of elements from the <see cref="ObservableCollection{T}"/>>. /// </summary> /// <param name="index">The zero-based starting index of the range of elements to remove.</param> /// <param name="count">The number of elements to remove.</param> /// <exception cref="ArgumentOutOfRangeException">The specified range is exceeding the collection.</exception> public void RemoveRange(int index, int count) { if (index < 0) throw new ArgumentOutOfRangeException(nameof(index)); if (count < 0) throw new ArgumentOutOfRangeException(nameof(count)); if (index + count > Count) throw new ArgumentOutOfRangeException(nameof(index)); if (count == 0) return; if (count == 1) { RemoveItem(index); return; } //Items will always be List<T>, see constructors var items = (List<T>)Items; List<T> removedItems = items.GetRange(index, count); CheckReentrancy(); items.RemoveRange(index, count); OnEssentialPropertiesChanged(); if (Count == 0) OnCollectionReset(); else OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, removedItems, index)); } /// <summary> /// Clears the current collection and replaces it with the specified collection, /// using the default <see cref="EqualityComparer{T}"/>. /// </summary> /// <param name="collection">The items to fill the collection with, after clearing it.</param> /// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception> public void ReplaceRange(IEnumerable<T> collection) { ReplaceRange(0, Count, collection, EqualityComparer<T>.Default); } /// <summary> /// Clears the current collection and replaces it with the specified collection, /// using the specified comparer to skip equal items. /// </summary> /// <param name="collection">The items to fill the collection with, after clearing it.</param> /// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to be used /// to check whether an item in the same location already existed before, /// which in case it would not be added to the collection, and no event will be raised for it.</param> /// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception> /// <exception cref="ArgumentNullException"><paramref name="comparer"/> is null.</exception> public void ReplaceRange(IEnumerable<T> collection, IEqualityComparer<T> comparer) { ReplaceRange(0, Count, collection, comparer); } /// <summary> /// Removes the specified range and inserts the specified collection, /// ignoring equal items (using <see cref="EqualityComparer{T}.Default"/>). /// </summary> /// <param name="index">The index of where to start the replacement.</param> /// <param name="count">The number of items to be replaced.</param> /// <param name="collection">The collection to insert in that location.</param> /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is out of range.</exception> /// <exception cref="ArgumentOutOfRangeException"><paramref name="count"/> is out of range.</exception> /// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception> public void ReplaceRange(int index, int count, IEnumerable<T> collection) { ReplaceRange(index, count, collection, EqualityComparer<T>.Default); } /// <summary> /// Removes the specified range and inserts the specified collection in its position, leaving equal items in equal positions intact. /// </summary> /// <param name="index">The index of where to start the replacement.</param> /// <param name="count">The number of items to be replaced.</param> /// <param name="collection">The collection to insert in that location.</param> /// <param name="comparer">The comparer to use when checking for equal items.</param> /// <exception cref="ArgumentOutOfRangeException"><paramref name="index"/> is out of range.</exception> /// <exception cref="ArgumentOutOfRangeException"><paramref name="count"/> is out of range.</exception> /// <exception cref="ArgumentNullException"><paramref name="collection"/> is null.</exception> /// <exception cref="ArgumentNullException"><paramref name="comparer"/> is null.</exception> public void ReplaceRange(int index, int count, IEnumerable<T> collection, IEqualityComparer<T> comparer) { if (index < 0) throw new ArgumentOutOfRangeException(nameof(index)); if (count < 0) throw new ArgumentOutOfRangeException(nameof(count)); if (index + count > Count) throw new ArgumentOutOfRangeException(nameof(index)); if (collection == null) throw new ArgumentNullException(nameof(collection)); if (comparer == null) throw new ArgumentNullException(nameof(comparer)); if (collection is ICollection<T> countable) { if (countable.Count == 0) { RemoveRange(index, count); return; } } else if (!ContainsAny(collection)) { RemoveRange(index, count); return; } if (index + count == 0) { InsertRange(0, collection); return; } if (!(collection is IList<T> list)) list = new List<T>(collection); using (BlockReentrancy()) using (DeferEvents()) { var rangeCount = index + count; var addedCount = list.Count; var changesMade = false; List<T> newCluster = null, oldCluster = null; int i = index; for (; i < rangeCount && i - index < addedCount; i++) { //parallel position T old = this[i], @new = list[i - index]; if (comparer.Equals(old, @new)) { OnRangeReplaced(i, newCluster, oldCluster); continue; } else { Items[i] = @new; if (newCluster == null) { Debug.Assert(oldCluster == null); newCluster = new List<T> { @new }; oldCluster = new List<T> { old }; } else { newCluster.Add(@new); oldCluster.Add(old); } changesMade = true; } } OnRangeReplaced(i, newCluster, oldCluster); //exceeding position if (count != addedCount) { var items = (List<T>)Items; if (count > addedCount) { var removedCount = rangeCount - addedCount; T[] removed = new T[removedCount]; items.CopyTo(i, removed, 0, removed.Length); items.RemoveRange(i, removedCount); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, removed, i)); } else { var k = i - index; T[] added = new T[addedCount - k]; for (int j = k; j < addedCount; j++) { T @new = list[j]; added[j - k] = @new; } items.InsertRange(i, added); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, added, i)); } OnEssentialPropertiesChanged(); } else if (changesMade) { OnIndexerPropertyChanged(); } } } #endregion Public Methods //------------------------------------------------------ // // Protected Methods // //------------------------------------------------------ #region Protected Methods /// <summary> /// Called by base class Collection<T> when the list is being cleared; /// raises a CollectionChanged event to any listeners. /// </summary> protected override void ClearItems() { if (Count == 0) return; CheckReentrancy(); base.ClearItems(); OnEssentialPropertiesChanged(); OnCollectionReset(); } /// <summary> /// Called by base class Collection<T> when an item is set in list; /// raises a CollectionChanged event to any listeners. /// </summary> protected override void SetItem(int index, T item) { if (Equals(this[index], item)) return; CheckReentrancy(); T originalItem = this[index]; base.SetItem(index, item); OnIndexerPropertyChanged(); OnCollectionChanged(NotifyCollectionChangedAction.Replace, originalItem, item, index); } /// <summary> /// Raise CollectionChanged event to any listeners. /// Properties/methods modifying this ObservableCollection will raise /// a collection changed event through this virtual method. /// </summary> /// <remarks> /// When overriding this method, either call its base implementation /// or call <see cref="BlockReentrancy"/> to guard against reentrant collection changes. /// </remarks> protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e) { if (_deferredEvents != null) { _deferredEvents.Add(e); return; } base.OnCollectionChanged(e); } protected virtual IDisposable DeferEvents() => new DeferredEventsCollection(this); #endregion Protected Methods //------------------------------------------------------ // // Private Methods // //------------------------------------------------------ #region Private Methods /// <summary> /// Helper function to determine if a collection contains any elements. /// </summary> /// <param name="collection">The collection to evaluate.</param> /// <returns></returns> private static bool ContainsAny(IEnumerable<T> collection) { using (IEnumerator<T> enumerator = collection.GetEnumerator()) return enumerator.MoveNext(); } /// <summary> /// Helper to raise Count property and the Indexer property. /// </summary> private void OnEssentialPropertiesChanged() { OnPropertyChanged(EventArgsCache.CountPropertyChanged); OnIndexerPropertyChanged(); } /// <summary> /// /// Helper to raise a PropertyChanged event for the Indexer property /// /// </summary> private void OnIndexerPropertyChanged() => OnPropertyChanged(EventArgsCache.IndexerPropertyChanged); /// <summary> /// Helper to raise CollectionChanged event to any listeners /// </summary> private void OnCollectionChanged(NotifyCollectionChangedAction action, object oldItem, object newItem, int index) => OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, newItem, oldItem, index)); /// <summary> /// Helper to raise CollectionChanged event with action == Reset to any listeners /// </summary> private void OnCollectionReset() => OnCollectionChanged(EventArgsCache.ResetCollectionChanged); /// <summary> /// Helper to raise event for clustered action and clear cluster. /// </summary> /// <param name="followingItemIndex">The index of the item following the replacement block.</param> /// <param name="newCluster"></param> /// <param name="oldCluster"></param> //TODO should have really been a local method inside ReplaceRange(int index, int count, IEnumerable<T> collection, IEqualityComparer<T> comparer), //move when supported language version updated. private void OnRangeReplaced(int followingItemIndex, ICollection<T> newCluster, ICollection<T> oldCluster) { if (oldCluster == null || oldCluster.Count == 0) { Debug.Assert(newCluster == null || newCluster.Count == 0); return; } OnCollectionChanged( new NotifyCollectionChangedEventArgs( NotifyCollectionChangedAction.Replace, new List<T>(newCluster), new List<T>(oldCluster), followingItemIndex - oldCluster.Count)); oldCluster.Clear(); newCluster.Clear(); } #endregion Private Methods //------------------------------------------------------ // // Private Types // //------------------------------------------------------ #region Private Types private sealed class DeferredEventsCollection : List<NotifyCollectionChangedEventArgs>, IDisposable { private readonly ObservableRangeCollection<T> _collection; public DeferredEventsCollection(ObservableRangeCollection<T> collection) { Debug.Assert(collection != null); Debug.Assert(collection._deferredEvents == null); _collection = collection; _collection._deferredEvents = this; } public void Dispose() { _collection._deferredEvents = null; foreach (var args in this) _collection.OnCollectionChanged(args); } } #endregion Private Types } /// <remarks> /// To be kept outside <see cref="ObservableCollection{T}"/>, since otherwise, a new instance will be created for each generic type used. /// </remarks> internal static class EventArgsCache { internal static readonly PropertyChangedEventArgs CountPropertyChanged = new PropertyChangedEventArgs("Count"); internal static readonly PropertyChangedEventArgs IndexerPropertyChanged = new PropertyChangedEventArgs("Item[]"); internal static readonly NotifyCollectionChangedEventArgs ResetCollectionChanged = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset); } }