调整大小WPF网格列在其他列儿童倒塌？(Resizing WPF Grid Column when

我有两个控件在Grid ，并需要做一个填补所有Grid的另一个后空间得到Collapseded ，我不知道什么Container我可以用，我试过StackPanel和DockPanel ，但我却无法找到一个好的solution.here是我的代码：

<Grid>
 <Grid.ColumnDefinitions>
    <ColumnDefinition Width="auto"/>
     <ColumnDefinition Width="auto"/>
 </Grid.ColumnDefinitions>
 <TextBox Grid.Column="0" Visibility="{Binding Istxt1Visible}"/>
 <TextBox Grid.Column="1" Visibility="{Binding Istxt2Visible}"/>
</Grid>

怎么样用一个转换器？如

在窗口资源

<Window.Resources>
    <local:VisibilityToColumnLengthConverter x:Key="visConv" />
</Window.Resources>

.....

<Grid >
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="{Binding ElementName=tb1, Path=Visibility, Converter={StaticResource visConv}}"/>
            <ColumnDefinition Width="{Binding ElementName=tb2, Path=Visibility, Converter={StaticResource visConv}}"/>
        </Grid.ColumnDefinitions>
        <TextBox Grid.Column="0" Visibility="collapsed" Name="tb1" />
        <TextBox Grid.Column="1" Visibility="Visible"   Name="tb2" />
    </Grid>

最后，转换器的代码

[ValueConversion(typeof(System.Windows.Visibility), typeof(System.Windows.GridLength))]
public class VisibilityToColumnLengthConverter : IValueConverter
{
    public object  Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        System.Windows.Visibility vis = (System.Windows.Visibility)value;

        if (vis == System.Windows.Visibility.Visible)
            return new System.Windows.GridLength(1, System.Windows.GridUnitType.Star);
        else
            return new System.Windows.GridLength(1, System.Windows.GridUnitType.Auto);
    }

    public object  ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}