<Grid x:Name="grid_1" Grid.Row="0" Margin="7, 7, 7, 50" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" > <TextBox x:Name="txtPONumbersStr" HorizontalAlignment="Center" TextWrapping="Wrap" VerticalAlignment="Top" Text="{Binding Path = PONumbersStr, Mode=TwoWay}" InputMethod.IsInputMethodEnabled ="False" PreviewTextInput="TextBox_PONumbersStr_PreviewTextInput" IsEnabled="{Binding Path=IsEnabled}" Width="{Binding ElementName=grid, Path=ActualWidth}" Height="{Binding ElementName=grid, Path=ActualHeight}" /> </Grid>, 调整代码, 使得TextBox的边框显示出来

可以在TextBox标签中添加一个Border标签，并将TextBox放在其中，代码如下：

<Grid x:Name="grid_1" Grid.Row="0" Margin="7, 7, 7, 50" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" >
    <Border BorderThickness="1" BorderBrush="Black">
        <TextBox x:Name="txtPONumbersStr" 
                 HorizontalAlignment="Center" 
                 TextWrapping="Wrap" 
                 VerticalAlignment="Top" 
                 Text="{Binding Path = PONumbersStr, Mode=TwoWay}"
                 InputMethod.IsInputMethodEnabled ="False"
                 PreviewTextInput="TextBox_PONumbersStr_PreviewTextInput"
                 IsEnabled="{Binding Path=IsEnabled}"
                 Width="{Binding ElementName=grid, Path=ActualWidth}"
                 Height="{Binding ElementName=grid, Path=ActualHeight}" />
    </Border>
</Grid>

在Border标签中设置BorderThickness和BorderBrush属性来定义边框的样式，可以根据需要进行调整。