如何对 TabControl 中的 TabItem 进行排序

Question

我有一个带有 Order 属性的 Page 类型的集合，我将 TabControl 的 ItemsSource 属性设置为 ObservableCollection。每当我更改实体的 Order 属性时我需要做什么 相关的 TabItem 位于正确的位置。

WPF XAML：

<TabControl Grid.Row="1" ItemsSource="{Binding Pages.ListViewModels}" SelectedItem="{Binding Pages.Current}"  >
    <TabControl.ContentTemplate>
        <DataTemplate>
            <views:EditPageView />
        </DataTemplate>
    </TabControl.ContentTemplate>
    <TabControl.ItemTemplate>
        <DataTemplate>                                    
            <TextBlock Text="{Binding Header}"/>
        </DataTemplate>
    </TabControl.ItemTemplate>
</TabControl>

C# 代码：

public class QuestionPageSection : INotifyPropertyChanged
{
    public virtual int Id { get; set; }
    public virtual string Header { get; set; }
    private int _Order;
    public virtual int Order
    {
        get
        {
            return _Order;
        }
        set
        {
            _Order = value;
            this.RaisePropertyChanged(() => this.Order , PropertyChanged);
        }
    }
    public event PropertyChangedEventHandler  PropertyChanged;
}

我想强制 TabControl 根据 Order 属性对 TabItems 进行排序。所以现在我有这些问题：

• 有没有办法以声明方式做到这一点？
• TabControl 有 SortColumn 属性吗？
• TabItem 是否有 TabOrder 属性？
• 是否有任何类型的集合可以侦听其子项以根据子项的属性自动对自身进行排序？

任何其他想法都会受到赞赏。

Answer 1

您只需要对 TabControl 绑定的集合进行排序

我一直讨厌 ObservableCollection 没有内置 Sort 方法，所以我通常使用我自己的继承自 ObservableCollection 的自定义类

public class ObservableCollectionEx<T> : ObservableCollection<T>
{
    public ObservableCollectionEx() : base() { }
    public ObservableCollectionEx(List<T> l) : base(l) { }
    public ObservableCollectionEx(IEnumerable<T> l) : base(l) { }

    #region IndexOf

    /// <summary>
    /// Returns the index of the first object which meets the specified function
    /// </summary>
    /// <param name="keySelector">A bool function to compare each Item by</param>
    /// <returns>The index of the first Item which matches the function</returns>
    public int IndexOf(Func<T, bool> compareFunction)
    {
        return Items.IndexOf(Items.FirstOrDefault(compareFunction));
    }

    #endregion

    #region Sorting

    /// <summary>
    /// Sorts the items of the collection in ascending order according to a key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
    /// <param name="keySelector">A function to extract a key from an item.</param>
    public void Sort<TKey>(Func<T, TKey> keySelector)
    {
        InternalSort(Items.OrderBy(keySelector));
    }

    /// <summary>
    /// Sorts the items of the collection in descending order according to a key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
    /// <param name="keySelector">A function to extract a key from an item.</param>
    public void SortDescending<TKey>(Func<T, TKey> keySelector)
    {
        InternalSort(Items.OrderByDescending(keySelector));
    }

    /// <summary>
    /// Sorts the items of the collection in ascending order according to a key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
    /// <param name="keySelector">A function to extract a key from an item.</param>
    /// <param name="comparer">An <see cref="IComparer{T}"/> to compare keys.</param>
    public void Sort<TKey>(Func<T, TKey> keySelector, IComparer<TKey> comparer)
    {
        InternalSort(Items.OrderBy(keySelector, comparer));
    }

    /// <summary>
    /// Moves the items of the collection so that their orders are the same as those of the items provided.
    /// </summary>
    /// <param name="sortedItems">An <see cref="IEnumerable{T}"/> to provide item orders.</param>
    private void InternalSort(IEnumerable<T> sortedItems)
    {
        var sortedItemsList = sortedItems.ToList();

        foreach (var item in sortedItemsList)
        {
            Move(IndexOf(item), sortedItemsList.IndexOf(item));
        }
    }

    #endregion
}

我可以这样使用它：

ListViewModels = GetListViewModels();
ListViewModels.Sort(p => p.Order);

Answer 2

您可以使用 CollectionViewSource 在 UI 端对 ObservableCollection 进行排序。以下是示例链接： http://msdn.microsoft.com/en-us /library/ms742542.aspx

Answer 3

谢谢 Rachel，你的解决方案给了我线索，但你的解决方案仍然是一个答案，因为每当我更改 Order 属性时我都可以手动调用 Sort 方法，但我想让它自动执行。所以我最终得到了你的代码的动态版本。

基于 Rachel，我找到了这个解决方案。

public class ObservableCollectionEx<T> : ObservableCollection<T>
{
    public ObservableCollectionEx() : base() { }

    public ObservableCollectionEx(List<T> l) : base(l) { }

    public ObservableCollectionEx(IEnumerable<T> l) : base(l) { }

    Func<IEnumerable<T>,IEnumerable<T>> sortFunction;
    Action reset;

    #region IndexOf

    /// <summary>
    /// Returns the index of the first object which meets the specified function
    /// </summary>
    /// <param name="keySelector">A bool function to compare each Item by</param>
    /// <returns>The index of the first Item which matches the function</returns>
    public int IndexOf(Func<T , bool> compareFunction)
    {
        return Items.IndexOf(Items.FirstOrDefault(compareFunction));
    }

    #endregion IndexOf

    #region Sorting

    /// <summary>
    /// Sorts the items of the collection in ascending order according to a key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
    /// <param name="keySelector">A function to extract a key from an item.</param>
    public void SetSort<TKey>(Func<T , TKey> keySelector)
    {
        sortFunction = list => list.OrderBy(keySelector);
        InternalSort();
        reset = () => SetSort(keySelector);
    }

    /// <summary>
    /// Sorts the items of the collection in descending order according to a key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
    /// <param name="keySelector">A function to extract a key from an item.</param>
    public void SetSortDescending<TKey>(Func<T , TKey> keySelector)
    {
        sortFunction = list => list.OrderByDescending(keySelector);
        InternalSort();
        reset = () => SetSortDescending(keySelector);
    }

    /// <summary>
    /// Sorts the items of the collection in ascending order according to a key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
    /// <param name="keySelector">A function to extract a key from an item.</param>
    /// <param name="comparer">An <see cref="IComparer{T}"/> to compare keys.</param>
    public void SetSort<TKey>(Func<T , TKey> keySelector , IComparer<TKey> comparer)
    {
        sortFunction = list => list.OrderBy(keySelector , comparer);
        InternalSort();
        reset = () => SetSort(keySelector , comparer);
    }

    /// <summary>
    /// Sorts the items of the collection in descending order according to a key.
    /// </summary>
    /// <typeparam name="TKey">The type of the key returned by <paramref name="keySelector"/>.</typeparam>
    /// <param name="keySelector">A function to extract a key from an item.</param>
    /// <param name="comparer">An <see cref="IComparer{T}"/> to compare keys.</param>
    public void SetSortDescending<TKey>(Func<T , TKey> keySelector , IComparer<TKey> comparer)
    {
        sortFunction = list => list.OrderByDescending(keySelector , comparer);
        InternalSort();
        reset = () => SetSortDescending(keySelector , comparer);
    }

    /// <summary>
    /// Moves the items of the collection so that their orders are the same as those of the items provided.
    /// </summary>
    private void InternalSort()
    {
        UpdateTracking(null , Items.ToList());
    }

    private void MoveItemToItsLocation(T item)
    {
        var sortListCache = sortFunction(Items).ToList();
        Move(IndexOf(item) , sortListCache.IndexOf(item));
    }

    #endregion Sorting

    public void UpdateTracking(IEnumerable<T> oldItems , IEnumerable<T> newItems)
    {
        if (sortFunction == null) return;

        PropertyChangedEventHandler changeTracker = (o , change) => { MoveItemToItsLocation((T)o); };
        Action<T> attachChangeTracker = o => o.ExecuteOnCast<INotifyPropertyChanged>(x => x.PropertyChanged += changeTracker);
        Action<T> detachChangeTracker = o => o.ExecuteOnCast<INotifyPropertyChanged>(x => x.PropertyChanged -= changeTracker);

        var greeting = new[] { attachChangeTracker , MoveItemToItsLocation };
        var farwell = new[] { detachChangeTracker };

        oldItems.ForEach(detachChangeTracker);
        newItems.ForEach(attachChangeTracker , MoveItemToItsLocation);
    }

    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        base.OnCollectionChanged(e);

        switch (e.Action) {
            case NotifyCollectionChangedAction.Add:
            case NotifyCollectionChangedAction.Remove:
            case NotifyCollectionChangedAction.Replace:
                UpdateTracking(e.OldItems.SafeGet(x => x.Cast<T>()) , e.NewItems.SafeGet(x => x.Cast<T>()));
                break;
            case NotifyCollectionChangedAction.Reset:
                UpdateTracking(Items.ToList() , null);
                if (reset != null)
                    reset();
                break;
            default:
                break;
        }
    }
}

我只做了一点更改，使其遵循基础集合中的更改，因此在对基础集合或基础集合中的任何元素进行任何更改后，它会自动对自身进行排序。