wpf 记一次诡异的PreviewMouseLeftButtonDown 无法触发问题

1、原始代码

<Grid  >
                                            <i:Interaction.Triggers>
                                                <i:EventTrigger EventName="PreviewMouseLeftButtonDown">
                                                    <i:InvokeCommandAction Command="{Binding DataContext.MouseLeftButtonDownCommand,RelativeSource={RelativeSource AncestorType=local:PermissionManagementView}}" CommandParameter="{Binding }"></i:InvokeCommandAction>
                                                </i:EventTrigger>
                                            </i:Interaction.Triggers>
                                            <Grid.ColumnDefinitions>
                                                    <!--需要预留一个-->
                                                    <ColumnDefinition   ></ColumnDefinition>
                                                    <ColumnDefinition   SharedSizeGroup="c1"  ></ColumnDefinition>
                                                    <ColumnDefinition   SharedSizeGroup="c2"  ></ColumnDefinition>
                                                    <ColumnDefinition   SharedSizeGroup="c3"  ></ColumnDefinition>
                                                    <ColumnDefinition  SharedSizeGroup="c4"   ></ColumnDefinition>
                                                    <ColumnDefinition  SharedSizeGroup="c5"  ></ColumnDefinition>
                                                    <ColumnDefinition  SharedSizeGroup="c6"  ></ColumnDefinition>
                                                    <ColumnDefinition  SharedSizeGroup="c7"  ></ColumnDefinition>
                                                    <ColumnDefinition  SharedSizeGroup="c8"   ></ColumnDefinition>
                                                    <ColumnDefinition  SharedSizeGroup="c9"   ></ColumnDefinition>
                                                </Grid.ColumnDefinitions> 
                                         
                                                
                                                <TextBlock    Grid.Column="0"  Text="{Binding Id}"  VerticalAlignment="Center"  ></TextBlock>

  </Grid  >

在Grid不加背景颜色的时候点击空白处 时不时无法触发隧道事件PreviewMouseLeftButtonDown

bug解决 增加一个透明背景颜色 触发正常! 

 Background="Transparent"

   <Grid  Background="Transparent">
       <i:Interaction.Triggers>
           <i:EventTrigger EventName="PreviewMouseLeftButtonDown">
               <i:InvokeCommandAction Command="{Binding DataContext.MouseLeftButtonDownCommand,RelativeSource={RelativeSource AncestorType=local:PermissionManagementView}}" CommandParameter="{Binding }"></i:InvokeCommandAction>
           </i:EventTrigger>
       </i:Interaction.Triggers>
       <Grid.ColumnDefinitions>
               <!--需要预留一个-->
               <ColumnDefinition   ></ColumnDefinition>
               <ColumnDefinition   SharedSizeGroup="c1"  ></ColumnDefinition>
               <ColumnDefinition   SharedSizeGroup="c2"  ></ColumnDefinition>
               <ColumnDefinition   SharedSizeGroup="c3"  ></ColumnDefinition>
               <ColumnDefinition  SharedSizeGroup="c4"   ></ColumnDefinition>
               <ColumnDefinition  SharedSizeGroup="c5"  ></ColumnDefinition>
               <ColumnDefinition  SharedSizeGroup="c6"  ></ColumnDefinition>
               <ColumnDefinition  SharedSizeGroup="c7"  ></ColumnDefinition>
               <ColumnDefinition  SharedSizeGroup="c8"   ></ColumnDefinition>
               <ColumnDefinition  SharedSizeGroup="c9"   ></ColumnDefinition>
           </Grid.ColumnDefinitions> 
    
           
           <TextBlock    Grid.Column="0"  Text="{Binding Id}"  VerticalAlignment="Center"  ></TextBlock>
 </Grid>

.cs代码

        private ICommand _MouseLeftButtonDownCommand;

        public ICommand MouseLeftButtonDownCommand =>
            _MouseLeftButtonDownCommand ?? (_MouseLeftButtonDownCommand = new DelegateCommand<object>(ExecuteMouseLeftButtonDownCommand));

        private void ExecuteMouseLeftButtonDownCommand(object obj)
        {
            var sysmenu = obj as SysMenu;
            if (sysmenu != null)
            {
                this.SelectSysMenu = sysmenu;
            }
        }