WPF之Visibility的基础用法

Visibility有三种用法，
第一个：Visible 元素在窗体中正常显示
第二个：Collaspsed 元素不显示，也不占用空间
第三个：Hidden 元素不显示，但是任然为它保留空间
我用Visibility=“Hidden”来隐藏我的页面

页面在DataGrid中用Visibility="Hidden"
XAML代码：
<Grid HorizontalAlignment="Center"VerticalAlignment="Center" Height="200" Width="200"Grid.ColumnSpan="8" Grid.RowSpan="6">
<DataGrid x:Name="DG_SP" IsReadOnly="True"AutoGenerateColumns="False" CanUserResizeColumns="False"CanUserResizeRows="False" SelectionMode="Single"CanUserReorderColumns="False" AlternationCount="2" RowHeaderWidth="0" CanUserAddRows="False"VerticalAlignment="Top" Visibility="Hidden"SelectedCellsChanged="DG_SP_SelectedCellsChanged">
<DataGrid.Background>
<LinearGradientBrushStartPoint="0,0" EndPoint="0,1">
<LinearGradientBrush.GradientStops>
<GradientStopColor="#FFE6F2F7" Offset="0"/>
<GradientStopColor="White" Offset="0.1"/>
<GradientStopColor="White" Offset="0.4"/>
<GradientStopColor="#FFE6F2F7" Offset="0.81"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
</DataGrid.Background>
<DataGrid.Columns >
<DataGridTextColumnHeader="行号" Binding="{Binding number}" Width="80"/>
<DataGridTextColumnHeader="编码" Visibility="Collapsed" Binding="{BindingCommodityInforID}" Width="10"/>
<DataGridTextColumnHeader="商品条码" Binding="{Binding CommodityCode}"Width="120" />
<!--<DataGridTextColumnHeader="打开" Visibility="Collapsed" Binding="{Bindingas_passenger_type_id}" Width="10" />-->
<DataGridTextColumnHeader="店内码" Binding="{Binding SecondCode}" Width="70" />
<DataGridTextColumnHeader="商品名称" Binding="{Binding CommodityName}" Width="80" />
<DataGridTextColumnHeader="数量" Binding="{Binding ss}" Width="70" />
<DataGridTextColumnHeader="金额" Binding="{Binding ee}" Width="70" />
</DataGrid.Columns>
</DataGrid>
</Grid>
按钮调用代码：
private void BTT_SP_Click(object sender,RoutedEventArgs e)
{
DG_SP.Visibility = Visibility.Visible;//显示页面
DataTable mm =myFrm_MerchandiseInventoryClient.Frm_CommodityInventoryEnquiry().Tables[0];
DG_SP.ItemsSource = mm.DefaultView;
}