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@ -13,24 +13,22 @@ using Avalonia.Controls.Utils; |
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namespace Avalonia.Controls |
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{ |
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/// <summary>
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/// Represents a standardized view of the supported interactions between a given ItemsSource
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/// object and an <see cref="ItemsRepeater"/> control.
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/// Represents a standardized view of the supported interactions between an items collection
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/// and an items control.
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/// </summary>
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/// <remarks>
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/// Components written to work with ItemsRepeater should consume the
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/// <see cref="ItemsRepeater.Items"/> via ItemsSourceView since this provides a normalized
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/// view of the Items. That way, each component does not need to know if the source is an
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/// IEnumerable, an IList, or something else.
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/// </remarks>
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public class ItemsSourceView : INotifyCollectionChanged, IDisposable |
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public class ItemsSourceView : IReadOnlyList<object?>, |
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INotifyCollectionChanged, |
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ICollectionChangedListener |
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{ |
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/// <summary>
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/// Gets an empty <see cref="ItemsSourceView"/>
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/// </summary>
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public static ItemsSourceView Empty { get; } = new ItemsSourceView(Array.Empty<object>()); |
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private IList? _inner; |
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private readonly IList _inner; |
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private NotifyCollectionChangedEventHandler? _collectionChanged; |
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private NotifyCollectionChangedEventHandler? _postCollectionChanged; |
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private bool _listening; |
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/// <summary>
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/// Initializes a new instance of the ItemsSourceView class for the specified data source.
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@ -38,15 +36,15 @@ namespace Avalonia.Controls |
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/// <param name="source">The data source.</param>
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public ItemsSourceView(IEnumerable source) |
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{ |
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source = source ?? throw new ArgumentNullException(nameof(source)); |
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_inner = source switch |
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{ |
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ItemsSourceView _ => throw new ArgumentException("Cannot wrap an existing ItemsSourceView.", nameof(source)), |
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ItemsSourceView => throw new ArgumentException("Cannot wrap an existing ItemsSourceView.", nameof(source)), |
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IList list => list, |
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INotifyCollectionChanged _ => throw new ArgumentException( |
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"Collection implements INotifyCollectionChanged by not IList.", |
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INotifyCollectionChanged => throw new ArgumentException( |
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"Collection implements INotifyCollectionChanged but not IList.", |
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nameof(source)), |
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IEnumerable<object> iObj => new List<object>(iObj), |
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null => throw new ArgumentNullException(nameof(source)), |
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_ => new List<object>(source.Cast<object>()) |
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}; |
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} |
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@ -56,26 +54,10 @@ namespace Avalonia.Controls |
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/// </summary>
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public int Count => Inner.Count; |
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/// <summary>
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/// Gets a value that indicates whether the items source can provide a unique key for each item.
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/// </summary>
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/// <remarks>
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/// TODO: Not yet implemented in Avalonia.
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/// </remarks>
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public bool HasKeyIndexMapping => false; |
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/// <summary>
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/// Gets the inner collection.
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/// </summary>
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public IList Inner |
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{ |
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get |
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{ |
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if (_inner is null) |
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ThrowDisposed(); |
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return _inner!; |
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} |
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} |
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public IList Inner => _inner; |
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/// <summary>
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/// Retrieves the item at the specified index.
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@ -84,6 +66,14 @@ namespace Avalonia.Controls |
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/// <returns>The item.</returns>
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public object? this[int index] => GetAt(index); |
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/// <summary>
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/// Gets a value that indicates whether the items source can provide a unique key for each item.
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/// </summary>
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/// <remarks>
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/// TODO: Not yet implemented in Avalonia.
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/// </remarks>
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internal bool HasKeyIndexMapping => false; |
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/// <summary>
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/// Occurs when the collection has changed to indicate the reason for the change and which items changed.
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/// </summary>
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@ -91,114 +81,133 @@ namespace Avalonia.Controls |
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{ |
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add |
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{ |
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if (_collectionChanged is null && Inner is INotifyCollectionChanged incc) |
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{ |
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incc.CollectionChanged += OnCollectionChanged; |
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} |
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AddListenerIfNecessary(); |
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_collectionChanged += value; |
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} |
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remove |
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{ |
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_collectionChanged -= value; |
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if (_collectionChanged is null && Inner is INotifyCollectionChanged incc) |
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{ |
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incc.CollectionChanged -= OnCollectionChanged; |
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} |
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RemoveListenerIfNecessary(); |
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} |
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} |
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/// <inheritdoc/>
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public void Dispose() |
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/// <summary>
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/// Occurs when a collection has finished changing and all <see cref="CollectionChanged"/>
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/// event handlers have been notified.
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/// </summary>
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internal event NotifyCollectionChangedEventHandler? PostCollectionChanged |
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{ |
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if (_inner is INotifyCollectionChanged incc) |
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add |
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{ |
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incc.CollectionChanged -= OnCollectionChanged; |
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AddListenerIfNecessary(); |
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_postCollectionChanged += value; |
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} |
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_inner = null; |
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remove |
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{ |
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_postCollectionChanged -= value; |
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RemoveListenerIfNecessary(); |
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} |
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} |
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/// <summary>
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/// Retrieves the item at the specified index.
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/// </summary>
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/// <param name="index">The index.</param>
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/// <returns>The item.</returns>
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public object? GetAt(int index) => Inner[index]; |
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public int IndexOf(object? item) => Inner.IndexOf(item); |
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public static ItemsSourceView GetOrCreate(IEnumerable? items) |
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private void AddListenerIfNecessary() |
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{ |
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if (items is ItemsSourceView isv) |
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if (!_listening) |
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{ |
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return isv; |
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if (_inner is INotifyCollectionChanged incc) |
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CollectionChangedEventManager.Instance.AddListener(incc, this); |
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_listening = true; |
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} |
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else if (items is null) |
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{ |
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return Empty; |
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} |
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else |
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} |
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private void RemoveListenerIfNecessary() |
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{ |
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if (_listening && _collectionChanged is null && _postCollectionChanged is null) |
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{ |
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return new ItemsSourceView(items); |
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if (_inner is INotifyCollectionChanged incc) |
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CollectionChangedEventManager.Instance.RemoveListener(incc, this); |
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_listening = false; |
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} |
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} |
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/// <summary>
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/// Retrieves the index of the item that has the specified unique identifier (key).
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/// Retrieves the item at the specified index.
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/// </summary>
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/// <param name="index">The index.</param>
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/// <returns>The key</returns>
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/// <remarks>
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/// TODO: Not yet implemented in Avalonia.
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/// </remarks>
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public string KeyFromIndex(int index) |
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{ |
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throw new NotImplementedException(); |
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} |
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/// <returns>The item.</returns>
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public object? GetAt(int index) => Inner[index]; |
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/// <summary>
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/// Determines the index of a specific item in the collection.
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/// </summary>
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/// <param name="item">The object to locate in the collection.</param>
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/// <returns>The index of value if found in the list; otherwise, -1.</returns>
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public int IndexOf(object? item) => Inner.IndexOf(item); |
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/// <summary>
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/// Retrieves the unique identifier (key) for the item at the specified index.
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/// Gets or creates an <see cref="ItemsSourceView"/> for the specified enumerable.
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/// </summary>
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/// <param name="key">The key.</param>
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/// <returns>The index.</returns>
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/// <param name="items">The enumerable.</param>
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/// <remarks>
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/// TODO: Not yet implemented in Avalonia.
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/// This method handles the following three cases:
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/// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
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/// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
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/// <see cref="ItemsSourceView"/>
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/// - Otherwise creates a new <see cref="ItemsSourceView"/>
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/// </remarks>
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public int IndexFromKey(string key) |
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public static ItemsSourceView GetOrCreate(IEnumerable? items) |
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{ |
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throw new NotImplementedException(); |
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return items switch |
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{ |
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ItemsSourceView isv => isv, |
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null => Empty, |
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_ => new ItemsSourceView(items) |
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}; |
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} |
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internal void AddListener(ICollectionChangedListener listener) |
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public IEnumerator<object?> GetEnumerator() |
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{ |
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if (Inner is INotifyCollectionChanged incc) |
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static IEnumerator<object> EnumerateItems(IList list) |
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{ |
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CollectionChangedEventManager.Instance.AddListener(incc, listener); |
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foreach (var o in list) |
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yield return o; |
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} |
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var inner = Inner; |
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return inner switch |
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{ |
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IEnumerable<object> e => e.GetEnumerator(), |
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_ => EnumerateItems(inner), |
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}; |
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} |
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internal void RemoveListener(ICollectionChangedListener listener) |
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IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator(); |
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void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e) |
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{ |
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if (Inner is INotifyCollectionChanged incc) |
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{ |
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CollectionChangedEventManager.Instance.RemoveListener(incc, listener); |
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} |
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} |
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protected void OnItemsSourceChanged(NotifyCollectionChangedEventArgs args) |
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void ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e) |
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{ |
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_collectionChanged?.Invoke(this, args); |
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_collectionChanged?.Invoke(this, e); |
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} |
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private void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e) |
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void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e) |
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{ |
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OnItemsSourceChanged(e); |
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_postCollectionChanged?.Invoke(this, e); |
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} |
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private void ThrowDisposed() => throw new ObjectDisposedException(nameof(ItemsSourceView)); |
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/// <summary>
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/// Retrieves the index of the item that has the specified unique identifier (key).
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/// </summary>
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/// <param name="index">The index.</param>
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/// <returns>The key</returns>
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/// <remarks>
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/// TODO: Not yet implemented in Avalonia.
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/// </remarks>
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internal string KeyFromIndex(int index) => throw new NotImplementedException(); |
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} |
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public class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T> |
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@ -227,9 +236,7 @@ namespace Avalonia.Controls |
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/// </summary>
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/// <param name="index">The index.</param>
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/// <returns>The item.</returns>
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#pragma warning disable CS8603
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public new T this[int index] => GetAt(index); |
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#pragma warning restore CS8603
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/// <summary>
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/// Retrieves the item at the specified index.
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@ -238,23 +245,44 @@ namespace Avalonia.Controls |
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/// <returns>The item.</returns>
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public new T GetAt(int index) => (T)Inner[index]!; |
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public IEnumerator<T> GetEnumerator() => Inner.Cast<T>().GetEnumerator(); |
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IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator(); |
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public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items) |
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public new IEnumerator<T> GetEnumerator() |
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{ |
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if (items is ItemsSourceView<T> isv) |
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static IEnumerator<T> EnumerateItems(IList list) |
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{ |
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return isv; |
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foreach (var o in list) |
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yield return (T)o; |
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} |
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else if (items is null) |
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var inner = Inner; |
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return inner switch |
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{ |
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return Empty; |
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} |
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else |
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IEnumerable<T> e => e.GetEnumerator(), |
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_ => EnumerateItems(inner), |
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}; |
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} |
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IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator(); |
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/// <summary>
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/// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
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/// </summary>
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/// <param name="items">The enumerable.</param>
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/// <remarks>
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/// This method handles the following three cases:
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/// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
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/// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
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/// <see cref="ItemsSourceView"/>
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/// - Otherwise creates a new <see cref="ItemsSourceView"/>
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/// </remarks>
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public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items) |
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{ |
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return items switch |
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{ |
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return new ItemsSourceView<T>(items); |
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} |
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ItemsSourceView<T> isv => isv, |
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null => Empty, |
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_ => new ItemsSourceView<T>(items) |
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}; |
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} |
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} |
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} |
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Steven Kirk
3 years ago