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/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Base / System / Collections / ObjectModel / ObservableCollection.cs / 1 / ObservableCollection.cs
//---------------------------------------------------------------------------- // //// Copyright (C) 2003 by Microsoft Corporation. All rights reserved. // // // // Description: Implementation of an Collectionimplementing INotifyCollectionChanged // to notify listeners of dynamic changes of the list. // // See spec at [....]/connecteddata/Specs/Collection%20Interfaces.mht // // History: // 11/22/2004 : [....] - created // //--------------------------------------------------------------------------- using System; using System.Collections; using System.Collections.Generic; using System.Collections.Specialized; using System.ComponentModel; using System.Windows; namespace System.Collections.ObjectModel { /// /// 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. /// [Serializable()] public class ObservableCollection: Collection , INotifyCollectionChanged, INotifyPropertyChanged { //----------------------------------------------------- // // Constructors // //----------------------------------------------------- #region Constructors /// /// Initializes a new instance of ObservableCollection that is empty and has default initial capacity. /// public ObservableCollection() : base() { } ////// Initializes a new instance of the ObservableCollection class /// that contains elements copied from the specified list /// /// The list whose elements are copied to the new list. ////// The elements are copied onto the ObservableCollection in the /// same order they are read by the enumerator of the list. /// ///list is a null reference public ObservableCollection(Listlist) : base((list != null) ? new List (list.Count) : list) { // Workaround for VSWhidbey bug 562681 (tracked by Windows bug 1369339). // We should be able to simply call the base(list) ctor. But Collection // doesn't copy the list (contrary to the documentation) - it uses the // list directly as its storage. So we do the copying here. // IList items = Items; if (list != null && items != null) { using (IEnumerator enumerator = list.GetEnumerator()) { while (enumerator.MoveNext()) { items.Add(enumerator.Current); } } } } #endregion Constructors //------------------------------------------------------ // // Public Methods // //----------------------------------------------------- #region Public Methods /// /// Move item at oldIndex to newIndex. /// public void Move(int oldIndex, int newIndex) { MoveItem(oldIndex, newIndex); } #endregion Public Methods //------------------------------------------------------ // // Public Events // //------------------------------------------------------ #region Public Events //----------------------------------------------------- #region INotifyPropertyChanged implementation ////// PropertyChanged event (per event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged { add { PropertyChanged += value; } remove { PropertyChanged -= value; } } #endregion INotifyPropertyChanged implementation //------------------------------------------------------ ///). /// /// Occurs when the collection changes, either by adding or removing an item. /// ////// see public virtual event NotifyCollectionChangedEventHandler CollectionChanged; #endregion Public Events //----------------------------------------------------- // // Protected Methods // //----------------------------------------------------- #region Protected Methods ////// /// Called by base class Collection<T> when the list is being cleared; /// raises a CollectionChanged event to any listeners. /// protected override void ClearItems() { CheckReentrancy(); base.ClearItems(); OnPropertyChanged(CountString); OnPropertyChanged(IndexerName); OnCollectionReset(); } ////// Called by base class Collection<T> when an item is removed from list; /// raises a CollectionChanged event to any listeners. /// protected override void RemoveItem(int index) { CheckReentrancy(); T removedItem = this[index]; base.RemoveItem(index); OnPropertyChanged(CountString); OnPropertyChanged(IndexerName); OnCollectionChanged(NotifyCollectionChangedAction.Remove, removedItem, index); } ////// Called by base class Collection<T> when an item is added to list; /// raises a CollectionChanged event to any listeners. /// protected override void InsertItem(int index, T item) { CheckReentrancy(); base.InsertItem(index, item); OnPropertyChanged(CountString); OnPropertyChanged(IndexerName); OnCollectionChanged(NotifyCollectionChangedAction.Add, item, index); } ////// Called by base class Collection<T> when an item is set in list; /// raises a CollectionChanged event to any listeners. /// protected override void SetItem(int index, T item) { CheckReentrancy(); T originalItem = this[index]; base.SetItem(index, item); OnPropertyChanged(IndexerName); OnCollectionChanged(NotifyCollectionChangedAction.Replace, originalItem, item, index); } ////// Called by base class ObservableCollection<T> when an item is to be moved within the list; /// raises a CollectionChanged event to any listeners. /// protected virtual void MoveItem(int oldIndex, int newIndex) { CheckReentrancy(); T removedItem = this[oldIndex]; base.RemoveItem(oldIndex); base.InsertItem(newIndex, removedItem); OnPropertyChanged(IndexerName); OnCollectionChanged(NotifyCollectionChangedAction.Move, removedItem, newIndex, oldIndex); } ////// Raises a PropertyChanged event (per protected virtual void OnPropertyChanged(PropertyChangedEventArgs e) { if (PropertyChanged != null) { PropertyChanged(this, e); } } ///). /// /// PropertyChanged event (per protected virtual event PropertyChangedEventHandler PropertyChanged; ///). /// /// Raise CollectionChanged event to any listeners. /// Properties/methods modifying this ObservableCollection will raise /// a collection changed event through this virtual method. /// ////// When overriding this method, either call its base implementation /// or call protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs e) { if (CollectionChanged != null) { using (BlockReentrancy()) { CollectionChanged(this, e); } } } ///to guard against reentrant collection changes. /// /// Disallow reentrant attempts to change this collection. E.g. a event handler /// of the CollectionChanged event is not allowed to make changes to this collection. /// ////// typical usage is to wrap e.g. a OnCollectionChanged call with a using() scope: /// protected IDisposable BlockReentrancy() { _monitor.Enter(); return _monitor; } ////// using (BlockReentrancy()) /// { /// CollectionChanged(this, new NotifyCollectionChangedEventArgs(action, item, index)); /// } ///
///Check and assert for reentrant attempts to change this collection. ///raised when changing the collection /// while another collection change is still being notified to other listeners protected void CheckReentrancy() { if (_monitor.Busy) { // we can allow changes if there's only one listener - the problem // only arises if reentrant changes make the original event args // invalid for later listeners. This keeps existing code working // (e.g. Selector.SelectedItems). if ((CollectionChanged != null) && (CollectionChanged.GetInvocationList().Length > 1)) throw new InvalidOperationException(SR.Get(SRID.ObservableCollectionReentrancyNotAllowed)); } } #endregion Protected Methods //----------------------------------------------------- // // Private Methods // //------------------------------------------------------ #region Private Methods ////// Helper to raise a PropertyChanged event />). /// private void OnPropertyChanged(string propertyName) { OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); } ////// Helper to raise CollectionChanged event to any listeners /// private void OnCollectionChanged(NotifyCollectionChangedAction action, object item, int index) { OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, item, index)); } ////// Helper to raise CollectionChanged event to any listeners /// private void OnCollectionChanged(NotifyCollectionChangedAction action, object item, int index, int oldIndex) { OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, item, index, oldIndex)); } ////// Helper to raise CollectionChanged event to any listeners /// private void OnCollectionChanged(NotifyCollectionChangedAction action, object oldItem, object newItem, int index) { OnCollectionChanged(new NotifyCollectionChangedEventArgs(action, newItem, oldItem, index)); } ////// Helper to raise CollectionChanged event with action == Reset to any listeners /// private void OnCollectionReset() { OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset)); } #endregion Private Methods //----------------------------------------------------- // // Private Types // //------------------------------------------------------ #region Private Types // this class helps prevent reentrant calls [Serializable()] private class SimpleMonitor : IDisposable { public void Enter() { ++ _busyCount; } public void Dispose() { -- _busyCount; } public bool Busy { get { return _busyCount > 0; } } int _busyCount; } #endregion Private Types //------------------------------------------------------ // // Private Fields // //----------------------------------------------------- #region Private Fields private const string CountString = "Count"; // This must agree with Binding.IndexerName. It is declared separately // here so as to avoid a dependency on PresentationFramework.dll. private const string IndexerName = "Item[]"; private SimpleMonitor _monitor = new SimpleMonitor(); #endregion Private Fields } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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