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 看起来新焦点元素接收KeyUp事件。 
 
 我所做的是订阅KeyDown事件，检查Tab键并将事件标记为已处理。 
 
protected override void OnAttached()
{
    var textBox = (TextBox)this.AssociatedObject;
    textBox.KeyDown += this.OnKeyDown;
    textBox.KeyUp += this.OnKeyUp;
    // don't forget to unsubscribe in OnDetached
}

private void OnKeyDown(object sender, KeyRoutedEventArgs e)
{
    if (e.Key == VirtualKey.Tab && !e.Handled)
    {
        e.Handled = this.Work(sender, e);
    }
}

private void OnKeyUp(object sender, KeyRoutedEventArgs e)
{
    if (e.Key != VirtualKey.Tab && !e.Handled)
    {
        e.Handled = this.Work(sender, e);
    }
}
 
 这是进行聚焦工作的方法。 在我知道怎么做之前，代码在OnKeyUp 。 
 
/// <returns>true if an action has been performed (focus next or execute command)</returns>
private bool Work(object sender, KeyRoutedEventArgs e)
{
    var isEnterKey = e.Key == VirtualKey.Enter;
    var isTabKey = e.Key == VirtualKey.Tab;

    if (/* there is something else to focus */)
    {
        // focus it
        return true;
    }

    return false;
}

Is looks like the newly focus element receives the KeyUp event.
 
What I did is subscribe to the KeyDown event, checked for the Tab key and marked the event as handled.
 
protected override void OnAttached()
{
    var textBox = (TextBox)this.AssociatedObject;
    textBox.KeyDown += this.OnKeyDown;
    textBox.KeyUp += this.OnKeyUp;
    // don't forget to unsubscribe in OnDetached
}

private void OnKeyDown(object sender, KeyRoutedEventArgs e)
{
    if (e.Key == VirtualKey.Tab && !e.Handled)
    {
        e.Handled = this.Work(sender, e);
    }
}

private void OnKeyUp(object sender, KeyRoutedEventArgs e)
{
    if (e.Key != VirtualKey.Tab && !e.Handled)
    {
        e.Handled = this.Work(sender, e);
    }
}
 
Here is the method that does the focusing work. The code was in OnKeyUp before I knew how to do.
 
/// <returns>true if an action has been performed (focus next or execute command)</returns>
private bool Work(object sender, KeyRoutedEventArgs e)
{
    var isEnterKey = e.Key == VirtualKey.Enter;
    var isTabKey = e.Key == VirtualKey.Tab;

    if (/* there is something else to focus */)
    {
        // focus it
        return true;
    }

    return false;
}