这个属性是什么意思呀
<StackPanel x:Name="LayoutRoot" Background="White">
<StackPanel Orientation="Horizontal">
<TextBlock Name="lbl_FirstName">First name</TextBlock>
<TextBox AutomationProperties.LabeledBy="{Binding ElementName=lbl_FirstName}" Name="tbFirstName" Width="100"/>
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Name="lbl_LastName">Last name</TextBlock>
<TextBox AutomationProperties.LabeledBy="{Binding ElementName=lbl_LastName}" Name="tbLastName" Width="100"/>
</StackPanel>
</StackPanel>