21

我有一个 ObservableCollection 和一个 WPF UserControl 数据绑定到它。控件是一个图表,它为 ObservableCollection 中的每个 BarData 类型的项目显示一个垂直条。

ObservableCollection<BarData>

class BarData
{
   public DateTime StartDate {get; set;}
   public double MoneySpent {get; set;}
   public double TotalMoneySpentTillThisBar {get; set;}
}

现在我想根据 StartDate 对 ObservableCollection 进行排序,以便 BarData 在集合中按 StartDate 的递增顺序排列。然后我可以像这样计算每个 BarData 中 TotalMoneySpentTillThisBar 的值 -

var collection = new ObservableCollection<BarData>();
//add few BarData objects to collection
collection.Sort(bar => bar.StartData);    // this is ideally the kind of function I was looking for which does not exist 
double total = 0.0;
collection.ToList().ForEach(bar => {
                                     bar.TotalMoneySpentTillThisBar = total + bar.MoneySpent;
                                     total = bar.TotalMoneySpentTillThisBar; 
                                   }
                            );

我知道我可以使用 ICollectionView 对数据进行排序、过滤以进行查看,但这不会改变实际的集合。我需要对实际集合进行排序,以便可以计算每个项目的 TotalMoneySpentTillThisBar。它的价值取决于收藏品的顺序。

谢谢。

4

6 回答 6

47

嗯,我给你的第一个问题是:你ObservableCollection的排序真的很重要,还是你真正想要的是将 GUI 中的显示排序?

我假设目标是有一个将“实时”更新的排序显示。然后我看到2个解决方案

  1. 得到ICollectionView你的ObservableCollection并对其进行排序,如此处所述 http://marlongrech.wordpress.com/2008/11/22/icollectionview-explained/

  2. 将您绑定ObservableCollection到 a CollectionViewsource,在其上添加排序,然后将其CollectionViewSource用作ItemSourcea ListView

IE:

添加这个命名空间

xmlns:scm="clr-namespace:System.ComponentModel;assembly=WindowsBase"

然后

<CollectionViewSource x:Key='src' Source="{Binding MyObservableCollection, ElementName=MainWindowName}">
    <CollectionViewSource.SortDescriptions>
        <scm:SortDescription PropertyName="MyField" />
    </CollectionViewSource.SortDescriptions>

</CollectionViewSource>

并像这样绑定

<ListView ItemsSource="{Binding Source={StaticResource src}}" >
于 2011-09-02T17:25:29.410 回答
18

我刚刚创建了一个扩展的类,ObservableCollection因为随着时间的推移,我还想要其他我习惯使用的功能List( Contains, IndexOf, AddRange, RemoveRange, 等)

我通常将它与类似的东西一起使用

MyCollection.Sort(p => p.Name);

这是我的排序实现

/// <summary>
/// Expanded ObservableCollection to include some List<T> Methods
/// </summary>
[Serializable]
public class ObservableCollectionEx<T> : ObservableCollection<T>
{

    /// <summary>
    /// Constructors
    /// </summary>
    public ObservableCollectionEx() : base() { }
    public ObservableCollectionEx(List<T> l) : base(l) { }
    public ObservableCollectionEx(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
}
于 2011-09-02T15:14:27.950 回答
14

对 ObservableCollection 进行排序的问题在于,每次更改集合时,都会触发一个事件。因此,对于从一个位置删除项目并将它们添加到另一个位置的排序,您最终将触发大量事件。

我认为你最好的办法是把这些东西以正确的顺序插入到 ObservableCollection 中。从集合中删除项目不会影响排序。我提出了一个快速扩展方法来说明

    public static void InsertSorted<T>(this ObservableCollection<T> collection, T item, Comparison<T> comparison)
    {
        if (collection.Count == 0)
            collection.Add(item);
        else
        {
            bool last = true;
            for (int i = 0; i < collection.Count; i++)
            {
                int result = comparison.Invoke(collection[i], item);
                if (result >= 1)
                {
                    collection.Insert(i, item);
                    last = false;
                    break;
                }
            }
            if (last)
                collection.Add(item);
        }
    }

因此,如果您要使用字符串(例如),代码将如下所示

        ObservableCollection<string> strs = new ObservableCollection<string>();
        Comparison<string> comparison = new Comparison<string>((s1, s2) => { return String.Compare(s1, s2); });
        strs.InsertSorted("Mark", comparison);
        strs.InsertSorted("Tim", comparison);
        strs.InsertSorted("Joe", comparison);
        strs.InsertSorted("Al", comparison);

编辑

如果您扩展 ObservableCollection 并提供您自己的插入/添加方法,您可以保持调用相同。像这样的东西:

public class BarDataCollection : ObservableCollection<BarData>
{
    private Comparison<BarData> _comparison = new Comparison<BarData>((bd1, bd2) => { return DateTime.Compare(bd1.StartDate, bd2.StartDate); });

    public new void Insert(int index, BarData item)
    {
        InternalInsert(item);
    }

    protected override void InsertItem(int index, BarData item)
    {
        InternalInsert(item);
    }

    public new void Add(BarData item)
    {
        InternalInsert(item);
    }

    private void InternalInsert(BarData item)
    {
        if (Items.Count == 0)
            Items.Add(item);
        else
        {
            bool last = true;
            for (int i = 0; i < Items.Count; i++)
            {
                int result = _comparison.Invoke(Items[i], item);
                if (result >= 1)
                {
                    Items.Insert(i, item);
                    last = false;
                    break;
                }
            }
            if (last)
                Items.Add(item);
        }
    }
}

插入索引被忽略。

        BarData db1 = new BarData(DateTime.Now.AddDays(-1));
        BarData db2 = new BarData(DateTime.Now.AddDays(-2));
        BarData db3 = new BarData(DateTime.Now.AddDays(1));
        BarData db4 = new BarData(DateTime.Now);
        BarDataCollection bdc = new BarDataCollection();
        bdc.Add(db1);
        bdc.Insert(100, db2);
        bdc.Insert(1, db3);
        bdc.Add(db4);
于 2011-09-02T15:00:27.530 回答
0

在不同的集合上使用 LINQ 对数据进行排序怎么样:

var collection = new List<BarData>();
//add few BarData objects to collection

// sort the data using LINQ
var sorted = from item in collection orderby item.StartData select item;

// create observable collection
var oc = new ObservableCollection<BarData>(sorted);

这对我有用。

于 2015-11-24T12:31:20.120 回答
0

我知道这是旧帖子,但我对大多数解决方案都不满意,因为它破坏了绑定。因此,如果有人遇到,这就是我所做的。您可以为更多属性排序进行更多重载。

这不会破坏绑定。

    public static void AddRangeSorted<T, TSort>(this ObservableCollection<T> collection, IEnumerable<T> toAdd, Func<T, TSort> sortSelector, OrderByDirection direction)
    {
        var sortArr = Enumerable.Concat(collection, toAdd).OrderBy(sortSelector, direction).ToList();
        foreach (T obj in toAdd.OrderBy(o => sortArr.IndexOf(o)).ToList())
        {
            collection.Insert(sortArr.IndexOf(obj), obj);
        }
    }

    public static void AddRangeSorted<T, TSort, TSort2>(this ObservableCollection<T> collection, IEnumerable<T> toAdd, Func<T, TSort> sortSelector, OrderByDirection direction, Func<T, TSort2> sortSelector2, OrderByDirection direction2)
    {
        var sortArr = Enumerable.Concat(collection, toAdd).OrderBy(sortSelector, direction).ThenBy(sortSelector2, direction2).ToList();
        foreach (T obj in toAdd.OrderBy(o=> sortArr.IndexOf(o)).ToList())
        {
            collection.Insert(sortArr.IndexOf(obj), obj);
        }
    }

和用法:

OrderLines.AddRangeSorted(toAdd,ol=>ol.ID, OrderByDirection.Ascending);
于 2021-03-15T19:05:00.547 回答
0

同样使用 LINQ/Extension 方法可以避免触发 NotifyPropertyChanged 事件,方法是不将源 col 设置为已排序的,但清除原始并添加已排序的项目。(如果实施,这将继续触发 Collectionchanged 事件)。

<Extension>
Public Sub SortByProp(Of T)(ByRef c As ICollection(Of T), PropertyName As String)
    Dim l = c.ToList
    Dim sorted = l.OrderBy(Function(x) x.GetType.GetProperty(PropertyName).GetValue(x))

    c.Clear()
    For Each i In sorted
        c.Add(i)
    Next

End Sub
于 2016-10-05T10:09:18.513 回答