.net 如何确定项目是否是WPF ItemTemplate中的最后一个项目？

我有一些XAML

<ItemsControl Name="mItemsControl">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBox Text="{Binding Mode=OneWay}" KeyUp="TextBox_KeyUp"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

我需要ISTExtBoxTheLastNeintheTemplate函数，但不知道如何编写。我该怎么写呢

我曾考虑过使用ItemsControl.ItemContainerGenerator，但无法将所有部分放在一起

谢谢

---

-迈克

我假设这是你正在研究的东西的简化版本。一个单向绑定到字符串集合的文本框对我来说没有意义

本例中的主要问题是使用简单字符串作为项源。我假设我们不能保证字符串是唯一的，所以我们不能从textbox.Text得出任何结论。此外，由于字符串是不可变的，我们不能使用字符串的实例来推断任何内容

解决方案的第一步是创建一个类来保存我们可以引用的数据。在这种情况下，这似乎有点愚蠢，因为它只包含一个字符串

    class MyData
    {
        public string Value { get; set; }
    }

您的第二个代码块变成：

    ObservableCollection<MyData> mCollection = new ObservableCollection<MyData>();

    public MainWindow()
    {
        InitializeComponent();

        this.mCollection.Add(new MyData { Value = "Test1" });
        this.mCollection.Add(new MyData { Value = "Test2" });
        this.mItemsControl.ItemsSource = this.mCollection;
    }

---

通过引用，我得到了一个不错的解决方案。不是很优雅，但对我来说很管用

    private void TextBox_KeyUp(object sender, KeyEventArgs e)
    {
        if (e.Key != Key.Enter)
        {
            return;
        }

        TextBox textbox = (TextBox)sender;

        var lastContainer = this.mItemsControl.ItemContainerGenerator.ContainerFromIndex(this.mItemsControl.Items.Count - 1);

        var visualContainer = (Visual)lastContainer;

        var containedTextbox = (TextBox)GetDescendantByType(visualContainer, typeof(TextBox));

        var isSame = textbox == containedTextbox;

        if (isSame)
        {
             this.mCollection.Add("A new textbox appears!");
        }
    }


    public static Visual GetDescendantByType(Visual element, Type type)
    {
        if (element.GetType() == type) return element;

        Visual foundElement = null;

        if (element is FrameworkElement)
            (element as FrameworkElement).ApplyTemplate();

        for (int i = 0;
            i < VisualTreeHelper.GetChildrenCount(element); i++)
        {
            Visual visual = VisualTreeHelper.GetChild(element, i) as Visual;
            foundElement = GetDescendantByType(visual, type);
            if (foundElement != null)
                break;
        }

        return foundElement;
    }

---

在我看来，这是视图模型中最好定义的行为：

public class ItemCollection : ObservableCollection<Item>
{
    public ItemCollection()
    {
        // this guarantees that any instance created always has at least one
        // item in it - you don't need this if you're creating instances in
        // code, but if you just create them in XAML you do.
        Item item = new Item(this);
        Add(item);
    }
}

public class Item
{
    internal Item(ItemCollection owner)
    {
        Owner = owner;
    }

    public bool IsLast
    {
        get
        {
            return Owner.LastOrDefault() == this;
        }
    }

    private ItemCollection Owner { get; set; }

    private string _Value;

    // here's the actual behavior:  if the last item in the collection is
    // given a non-empty Value, a new item gets added after it.
    public string Value
    {
        get { return _Value; }
        set
        {
            _Value = value;
            if (IsLast && !String.IsNullOrEmpty(_Value))
            {
                Owner.Add(new Item(Owner));
            }
        }
    }
}

使用KeyUp事件处理程序：

private void TextBox_KeyUp(object sender, KeyEventArgs e)
{
    if (e.Key != Key.Enter)
    {
        return;
    }

    TextBox t = (TextBox)sender;
    BindingExpression be = t.GetBindingExpression(TextBox.TextProperty);
    be.UpdateSource();
}

    private void TextBox_KeyUp(object sender, KeyEventArgs e)
    {
        if (e.Key != Key.Enter)
        {
            return;
        }

        TextBox textbox = (TextBox)sender;

        if (mItemsControl.Items.IndexOf(textbox.Tag) == mItemsControl.Items.Count - 1)
        {
            this.mCollection.Add(new MyData() { Value = "A new textbox appears!" });
        }
    }

    private void TextBox_KeyUp(object sender, KeyEventArgs e)
    {
        if (e.Key != Key.Enter)
        {
            return;
        }

        TextBox textbox = (TextBox)sender;

        var lastContainer = this.mItemsControl.ItemContainerGenerator.ContainerFromIndex(this.mItemsControl.Items.Count - 1);

        var visualContainer = (Visual)lastContainer;

        var containedTextbox = (TextBox)GetDescendantByType(visualContainer, typeof(TextBox));

        var isSame = textbox == containedTextbox;

        if (isSame)
        {
             this.mCollection.Add("A new textbox appears!");
        }
    }


    public static Visual GetDescendantByType(Visual element, Type type)
    {
        if (element.GetType() == type) return element;

        Visual foundElement = null;

        if (element is FrameworkElement)
            (element as FrameworkElement).ApplyTemplate();

        for (int i = 0;
            i < VisualTreeHelper.GetChildrenCount(element); i++)
        {
            Visual visual = VisualTreeHelper.GetChild(element, i) as Visual;
            foundElement = GetDescendantByType(visual, type);
            if (foundElement != null)
                break;
        }

        return foundElement;
    }

public class ItemCollection : ObservableCollection<Item>
{
    public ItemCollection()
    {
        // this guarantees that any instance created always has at least one
        // item in it - you don't need this if you're creating instances in
        // code, but if you just create them in XAML you do.
        Item item = new Item(this);
        Add(item);
    }
}

public class Item
{
    internal Item(ItemCollection owner)
    {
        Owner = owner;
    }

    public bool IsLast
    {
        get
        {
            return Owner.LastOrDefault() == this;
        }
    }

    private ItemCollection Owner { get; set; }

    private string _Value;

    // here's the actual behavior:  if the last item in the collection is
    // given a non-empty Value, a new item gets added after it.
    public string Value
    {
        get { return _Value; }
        set
        {
            _Value = value;
            if (IsLast && !String.IsNullOrEmpty(_Value))
            {
                Owner.Add(new Item(Owner));
            }
        }
    }
}

<DataTemplate DataType="{x:Type local:Item}">
    <TextBox Text="{Binding Value, Mode=TwoWay, UpdateSourceTrigger=Explicit}"
             KeyUp="TextBox_KeyUp"/>
</DataTemplate>

private void TextBox_KeyUp(object sender, KeyEventArgs e)
{
    if (e.Key != Key.Enter)
    {
        return;
    }

    TextBox t = (TextBox)sender;
    BindingExpression be = t.GetBindingExpression(TextBox.TextProperty);
    be.UpdateSource();
}