看名字就知道，它是一个弹出控件，顾名思义，我们可以用它来实现类似Combobox那种，点击后弹出下面选项列表的操作。

记录：

需求：有一个文本框 ，鼠标点击后，弹出一个Popup。

我编写了以下xaml

<Grid><TextBox PreviewMouseDown="text_PreviewMouseDown" x:Name="text" Text="666" BorderBrush="Red" BorderThickness="1" HorizontalAlignment="Left" VerticalAlignment="Top"Width="100" FontSize="30" HorizontalContentAlignment="Center" VerticalContentAlignment="Center"/><Popup Placement="Bottom" PlacementTarget="{Binding ElementName=text}"IsOpen="{Binding IsOpen1}"AllowsTransparency="True" StaysOpen="False" Width="200" Height="200"><Border Margin="10" Background="Green"><TextBox Text="弹出内容1" FontSize="30" HorizontalAlignment="Center" VerticalAlignment="Center"/></Border></Popup>
</Grid>

这时，奇怪的现象出现了，我鼠标点击textbox后，一松开，popup就消失了。。。

经过一番研究，发现。

问题出在textbox的点击事件上，在PreviewMouseDown事件执行完毕之后，焦点会移到textbox上，这里popup就失去焦点了。。

编写以下MainWindow.xaml:

<Window x:Class="wpfcore.MainWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:local="clr-namespace:wpfcore"mc:Ignorable="d"Title="MainWindow" Height="450" Width="800"><Grid><Grid.ColumnDefinitions><ColumnDefinition/><ColumnDefinition/></Grid.ColumnDefinitions><Grid><TextBox PreviewMouseUp="text_PreviewMouseDown" x:Name="text" Text="666" BorderBrush="Red" BorderThickness="1" HorizontalAlignment="Left" VerticalAlignment="Top"Width="100" FontSize="30" HorizontalContentAlignment="Center" VerticalContentAlignment="Center"/><Popup Placement="Bottom" PlacementTarget="{Binding ElementName=text}"IsOpen="{Binding IsOpen1}"AllowsTransparency="True" StaysOpen="False" Width="200" Height="200"><Border Margin="10" Background="Green"><TextBox Text="弹出内容1" FontSize="30" HorizontalAlignment="Center" VerticalAlignment="Center"/></Border></Popup></Grid><Grid Grid.Column="1"><TextBlock MouseUp="textBlock_PreviewMouseDown" x:Name="textblock" Text="666" Background="LightBlue" HorizontalAlignment="Left" VerticalAlignment="Top"Width="100" FontSize="30" TextAlignment="Center"/><Popup Placement="Bottom" PlacementTarget="{Binding ElementName=textblock}"IsOpen="{Binding IsOpen2}"AllowsTransparency="True" StaysOpen="False" Width="200" Height="200"><Border Margin="10" Background="Green"><TextBox Text="弹出内容2" FontSize="30" HorizontalAlignment="Center" VerticalAlignment="Center"/></Border></Popup></Grid></Grid>
</Window>

MainWindow.cs代码如下：

using System.Windows;
using System.Windows.Input;namespace wpfcore
{public partial class MainWindow : Window{public bool IsOpen1{get { return (bool)GetValue(IsOpen1Property); }set { SetValue(IsOpen1Property, value); }}public static readonly DependencyProperty IsOpen1Property =DependencyProperty.Register("IsOpen1", typeof(bool), typeof(MainWindow), new PropertyMetadata(false));public bool IsOpen2{get { return (bool)GetValue(IsOpen2Property); }set { SetValue(IsOpen2Property, value); }}public static readonly DependencyProperty IsOpen2Property =DependencyProperty.Register("IsOpen2", typeof(bool), typeof(MainWindow), new PropertyMetadata(false));public MainWindow(){InitializeComponent();DataContext = this;}private void text_PreviewMouseDown(object sender, MouseButtonEventArgs e){IsOpen1 = true;}private void textBlock_PreviewMouseDown(object sender, MouseButtonEventArgs e){IsOpen2 = true;}}
}

通过对比可以发现，使用一个TextBlock的效果比textbox好多了。。

以下是对比效果：

记录下来，备查。