c# - 扩展 Wpf Treeview 以支持排序

Question

您好，我创建了这个小示例，我想扩展它以支持排序。

public class Country
{
    public string Name { get; set; }
    public int SortOrder { get; set; }
}

我的 xaml:

<TreeView Name="CountryTreeView" ItemsSource="{Binding}">
  <TreeView.ItemTemplate>
    <DataTemplate>
      <TextBlock Text="{Binding Path=Name}"/>
    </DataTemplate>
  </TreeView.ItemTemplate>
</TreeView>

以及代码隐藏:

readonly ObservableCollection<Country> Countries;

public MainWindow()
{
   InitializeComponent();

   Countries = new ObservableCollection<Country>
   {
       new Country{Name = "Denmark", SortOrder = 0},
       new Country{Name = "Norway", SortOrder = 1},
       new Country{Name = "Sweden", SortOrder = 2},
       new Country{Name = "Iceland", SortOrder = 3},
       new Country{Name = "Greenland", SortOrder = 4},
   };

   CountryTreeView.DataContext = Countries;
}

我想让 Treeview 根据 SortOrder 值对 Countries 进行排序。

它需要能够即时执行此操作。因此，例如，如果我将 SortOrder = 10 更改为 Name = "Denmark"，TreeView 将自动反射(reflect)这一点。

Answer 1

我认为 TreeView 没有默认排序。您可以在将项目输入集合之前对其进行排序，或者覆盖 ObservableCollection 以包含 Sort 方法。

我在我的一个项目中覆盖了它:

public class SortableObservableCollection<T> : ObservableCollection<T>
{
    // Constructors
    public SortableObservableCollection() : base(){}
    public SortableObservableCollection(List<T> l) : base(l){}
    public SortableObservableCollection(IEnumerable<T> l) :base (l) {}

    #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 // Sorting
}

然后您可以通过调用类似

的方式对其进行排序

Countries.Sort(country => country.SortOrder);

我喜欢覆盖它，因为它让我可以向它添加额外的功能，例如 IndexOf 或 AddRange/RemoveRange