133 lines
3.1 KiB
C#
133 lines
3.1 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Collections.ObjectModel;
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using System.Collections.Specialized;
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using System.ComponentModel;
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namespace Microsoft.Research.DynamicDataDisplay.Common
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{
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/// <summary>
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/// This is a base class for some of collections in DynamicDataDisplay assembly.
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/// It provides means to be notified when item adding and added events, which enables successors to, for example,
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/// check if adding item is not equal to null.
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/// </summary>
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/// <typeparam name="T"></typeparam>
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public abstract class D3Collection<T> : ObservableCollection<T>
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{
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#region Overrides
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protected override void InsertItem(int index, T item)
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{
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OnItemAdding(item);
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base.InsertItem(index, item);
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OnItemAdded(item);
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}
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protected override void ClearItems()
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{
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foreach (var item in Items)
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{
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OnItemRemoving(item);
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}
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base.ClearItems();
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}
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protected override void RemoveItem(int index)
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{
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T item = Items[index];
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OnItemRemoving(item);
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base.RemoveItem(index);
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}
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protected override void SetItem(int index, T item)
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{
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T oldItem = Items[index];
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OnItemRemoving(oldItem);
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OnItemAdding(item);
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base.SetItem(index, item);
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OnItemAdded(item);
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}
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protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
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{
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attemptsToRaiseEvent++;
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if (raiseCollectionChangedEvent)
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{
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base.OnCollectionChanged(e);
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}
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}
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#endregion // end of Overrides
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/// <summary>
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/// Called before item added to collection. Enables to perform validation.
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/// </summary>
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/// <param name="item">The adding item.</param>
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protected virtual void OnItemAdding(T item) { }
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/// <summary>
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/// Called when item is added.
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/// </summary>
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/// <param name="item">The added item.</param>
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protected virtual void OnItemAdded(T item) { }
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/// <summary>
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/// Called when item is being removed, but before it is actually removed.
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/// </summary>
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/// <param name="item">The removing item.</param>
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protected virtual void OnItemRemoving(T item) { }
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#region Public
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int attemptsToRaiseEvent = 0;
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bool raiseCollectionChangedEvent = true;
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public void BeginUpdate()
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{
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attemptsToRaiseEvent = 0;
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raiseCollectionChangedEvent = false;
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}
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public void EndUpdate(bool raiseReset)
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{
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raiseCollectionChangedEvent = true;
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if (attemptsToRaiseEvent > 0 && raiseReset)
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{
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OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
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}
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}
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public IDisposable BlockEvents(bool raiseReset)
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{
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return new EventBlocker<T>(this, raiseReset);
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}
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private sealed class EventBlocker<TT> : IDisposable
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{
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private readonly D3Collection<TT> collection;
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private readonly bool raiseReset = true;
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public EventBlocker(D3Collection<TT> collection, bool raiseReset)
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{
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this.collection = collection;
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this.raiseReset = raiseReset;
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collection.BeginUpdate();
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}
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#region IDisposable Members
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public void Dispose()
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{
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collection.EndUpdate(raiseReset);
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}
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#endregion
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}
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#endregion // end of Public
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}
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}
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