如何使WPF Combobox的Dropdown保持打开和放置

Question

我希望Combobox可以编辑,并且下拉保持打开状态.

目前已设置这些属性:

IsEditable="True" IsDropDownOpen="True" StaysOpenOnEdit="True" 

每当用户单击输入文本框或焦点更改为其他控件时,dorpdown将关闭.所以我更新了模板(WPF主题中包含的模板:BureauBlue),以便Popup IsOpen="true"在此特定情况下使下拉列表保持打开状态,但现在当用户拖动并移动窗口的位置时,下拉列表将不会自动更新其位置并保持在旧职位.

如何在打开时自动更新其位置？

Answer 1

你可以使用这里描述的技巧:http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/27950e73-0007-4e0b-9f00-568d2db1d979

我创建了一个Blend行为,可以很容易地使用任何弹出窗口:

/// <summary>
/// A behavior that forces the associated popup to update its position when the <see cref="Popup.PlacementTarget"/>
/// location has changed.
/// </summary>
public class AutoRepositionPopupBehavior : Behavior<Popup> {
    public Point StartPoint = new Point(0, 0);
    public Point EndPoint = new Point(0, 0);

    protected override void OnAttached() {
        base.OnAttached();

        if (AssociatedObject.PlacementTarget != null) {
            AssociatedObject.PlacementTarget.LayoutUpdated += OnPopupTargetLayoutUpdated;
        }
    }

    void OnPopupTargetLayoutUpdated(object sender, EventArgs e) {
        if (AssociatedObject.IsOpen) {
            ResetPopUp();
        }
    }

    public void ResetPopUp() {
        // The following trick that forces the popup to change it's position was taken from here:
        // http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/27950e73-0007-4e0b-9f00-568d2db1d979
        Random random = new Random();
        AssociatedObject.PlacementRectangle = new Rect(new Point(random.NextDouble() / 1000, 0), new Size(75, 25));
    }
}

以下是如何应用行为的示例:

<Popup ...>
    <i:Interaction.Behaviors>
        <Behaviors:AutoRepositionPopupBehavior />
    </i:Interaction.Behaviors>
</Popup>