一：首先對MvvmLight裡的ViewModel進行封裝    封裝完畢後讓ViewModel繼承DialogViewModel

  public class DialogViewModel : ViewModelBase
    {

        public void PreviewKeyDownEvent(object sender,KeyEventArgs e)
        {
            TextBox text = sender as TextBox;
            if (e.Key > Key.D9 || e.Key > Key.NumPad9 && e.Key != Key.Enter || e.Key == Key.Space)
            {
                e.Handled = true;
            }
        }

    }
 

二：在xmal裡面進行Binding

<UserControl
	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:vm="clr-namespace:YunSuo.MonitorSystem.ViewModel"
	xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" 
    xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
    xmlns:Custom="http://www.galasoft.ch/mvvmlight"
   xmlns:local="clr-namespace:YunSuo.MonitorSystem"
	x:Class="YunSuo.MonitorSystem.MonitorSystemUI">

    <UserControl.Resources>
        <DataTemplate x:Key="alarmText">
            <TextBox Name="txtAlarm" KeyDown="txtAlarm_KeyDown"   Style="{DynamicResource textStyle}" Margin="10 0 0 0" Text="{Binding DiskAlarm.threshold}">
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="PreviewKeyDown" SourceName="txtAlarm">
                        <ei:CallMethodAction MethodName="PreviewKeyDownEvent" TargetObject="{Binding ElementName=MonitorSystem, Path=DataContext}"/>
                    </i:EventTrigger>
                    <i:EventTrigger EventName="MouseEnter">
                        <Custom:EventToCommand Command="{Binding Mode=OneWay, Path=DataContext.MouseEnterCommand, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}}"
                                                   CommandParameter="{Binding Path=DataContext, ElementName=txtAlarm}"/>
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </TextBox>
        </DataTemplate>
    </UserControl.Resources>
		
</UserControl>