WPF组合框MaxDropDownItems [英] WPF ComboBox MaxDropDownItems

问题描述

反正是有设置的下拉项的最大数量，而不是最大下拉高度WPF？
谢谢！
-Kevin

Is there anyway to set the maximum number of drop down items rather than the max drop down height in WPF? Thanks! -Kevin

推荐答案

这问题也许仅是有意义的，如果所有的项目都具有相同的高度。否则，因为滚动你的组合框上下，看你的组合框将得到更大和更小的滚动项目列表中的不同部分。

This question may only be meaningful if all of your items have the same height. Otherwise as you scroll your ComboBox up and down to see different portions of the item list your ComboBox would get bigger and smaller as you scroll.

如果您的所有项目的是的同一高度，这是很容易做到这一点使用附加属性：

If all of your items are the same height, it's very easy to do this using an attached property:

public class ComboBoxHelper : DependencyObject
{
  public static int GetMaxDropDownItems(DependencyObject obj) { return (int)obj.GetValue(MaxDropDownItemsProperty); }
  public static void SetMaxDropDownItems(DependencyObject obj, int value) { obj.SetValue(MaxDropDownItemsProperty, value); }
  public static readonly DependencyProperty MaxDropDownItemsProperty = DependencyProperty.RegisterAttached("MaxDropDownItems", typeof(int), typeof(ComboBoxHelper), new PropertyMetadata
  {
    PropertyChangedCallback = (obj, e) =>
    {
      var box = (ComboBox)obj;
      box.DropDownOpened += UpdateHeight;
      if(box.IsDropDownOpen) UpdateHeight(box, null);
    }
  });

  private static void UpdateHeight(object sender, EventArgs e)
  {
    var box = (ComboBox)sender;
    box.Dispatcher.BeginInvoke(DispatcherPriority.Input, new Action(() =>
      {
        var container = box.ItemContainerGenerator.ContainerFromIndex(0) as UIElement;
        if(container!=null && container.RenderSize.Height>0)
          box.MaxDropDownHeight = container.RenderSize.Height * GetMaxDropDownItems(box);
      }));
  }
}

通过这个属性，你可以这样写：

With this property you can write:

<ComboBox ...
   my:ComboBoxHelper.MaxDropDownItems="8" />

这篇关于WPF组合框MaxDropDownItems的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！