C# 如何在 ObservableCollection 的开头插入一个项目？

How to insert an item at the beginning of an ObservableCollection?

提问by Jason94

How can I do that? I need a list (of type ObservableCollection) where the latest item is first.

我怎样才能做到这一点？我需要一个列表（类型ObservableCollection），其中最新的项目是第一个。

采纳答案by Dmitry Reznik

Try using

尝试使用

collection.Insert(0, item);

This would add item to the beginning of the collection (while Add adds to the end). More info here.

这会将 item 添加到集合的开头（而 Add 添加到末尾）。更多信息在这里。

回答by Kevin

You should use a stack instead.

您应该改用堆栈。

This is based on Observable Stack and Queue

这是基于Observable Stack 和 Queue

Create an observable Stack, where stack is always last in first out (LIFO).

创建一个可观察的堆栈，其中堆栈总是后进先出（LIFO）。

from Sascha Holl

来自萨沙霍尔

public class ObservableStack<T> : Stack<T>, INotifyCollectionChanged, INotifyPropertyChanged
{
    public ObservableStack()
    {
    }

    public ObservableStack(IEnumerable<T> collection)
    {
        foreach (var item in collection)
            base.Push(item);
    }

    public ObservableStack(List<T> list)
    {
        foreach (var item in list)
            base.Push(item);
    }


    public new virtual void Clear()
    {
        base.Clear();
        this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }

    public new virtual T Pop()
    {
        var item = base.Pop();
        this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, item));
        return item;
    }

    public new virtual void Push(T item)
    {
        base.Push(item);
        this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item));
    }


    public virtual event NotifyCollectionChangedEventHandler CollectionChanged;


    protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        this.RaiseCollectionChanged(e);
    }

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        this.RaisePropertyChanged(e);
    }


    protected virtual event PropertyChangedEventHandler PropertyChanged;


    private void RaiseCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        if (this.CollectionChanged != null)
            this.CollectionChanged(this, e);
    }

    private void RaisePropertyChanged(PropertyChangedEventArgs e)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, e);
    }


    event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged
    {
        add { this.PropertyChanged += value; }
        remove { this.PropertyChanged -= value; }
    }
}

This calls INotifyCollectionChanged, does the same as a ObservableCollection, but in a stack manner.

这将调用 INotifyCollectionChanged，与 ObservableCollection 的作用相同，但采用堆栈方式。

回答by Samet Dumankaya

you can try this

你可以试试这个

collection.insert(0,collection.ElementAt(collection.Count - 1));

collection.insert(0,collection.ElementAt(collection.Count - 1));