Mvvm KeyDown的实现以及TextBox绑定的属性不更新问题的解决

今天写程序的时候遇到了个问题：使用mvvm给TextBox在vm层实现KeyDown键盘事件时，TextBox绑定的vm层属性不更新。

但在TextBox下加个按钮时就更新了。这个问题困扰了我好一会，最后才想起来是更新时机没有给定，所以默认的是LostFocus，故改为PropertyChanged就好了。

 1 <Window x:Class="TestDemo1.MainWindow"
 2         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4         xmlns:cmd="http://www.galasoft.ch/mvvmlight"
 5         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
 6         xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
 7         xmlns:ignore="http://www.galasoft.ch/ignore"
 8         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 9         Title="MVVM Light Application"
10         Width="300"
11         Height="300"
12         DataContext="{Binding Main,
13                               Source={StaticResource Locator}}"
14         mc:Ignorable="d ignore">
15
16     <Window.Resources>
17         <ResourceDictionary>
18             <ResourceDictionary.MergedDictionaries>
19                 <ResourceDictionary Source="Skins/MainSkin.xaml" />
20             </ResourceDictionary.MergedDictionaries>
21         </ResourceDictionary>
22     </Window.Resources>
23
24     <Grid x:Name="LayoutRoot">
25         <StackPanel>
26             <TextBlock Margin="0,50,0,0"
27                        HorizontalAlignment="Center"
28                        VerticalAlignment="Center"
29                        FontWeight="Bold"
30                        Foreground="Purple"
31                        Text="{Binding WelcomeTitle}"
32                        TextWrapping="Wrap" />
33             <TextBox Margin="20" Text="{Binding MyField, UpdateSourceTrigger=PropertyChanged}">
34                 <i:Interaction.Triggers>
35                     <i:EventTrigger EventName="KeyDown">
36                         <cmd:EventToCommand Command="{Binding MyTestCommand}" />
37                     </i:EventTrigger>
38                 </i:Interaction.Triggers>
39             </TextBox>
40             <Button Height="20"
41                     Command="{Binding CmdBtn}"
42                     Content="Button" />
43         </StackPanel>
44     </Grid>
45 </Window>

链接：http://files.cnblogs.com/files/zhangyongheng/TestDemo1.rar