关于wpf中binding如何给converter传递控件

<Popup x:Name="dispatchPop"
                   PlacementTarget="{Binding ElementName=griddatalist}"
                   StaysOpen="True"
                   IsOpen="False"
                   Width="{Binding ElementName=griddatalist, Path=ActualWidth, Converter={StaticResource actualWidth}}" Height="20"
                   Placement="Left"
                   Placement="Bottom"
                   PopupAnimation="Fade"
                   AllowsTransparency = "True"
                   x:Name="dispatchPop"
                   HorizontalOffset="{Binding ElementName=griddatalist, Path=ActualWidth,UpdateSourceTrigger=PropertyChanged}"
                   >


                <Popup.VerticalOffset>
                    <MultiBinding Converter="{StaticResource ver}">
                        <Binding ElementName="griddatalist,Path=DataContext,UpdateSourceTrigger=PropertyChanged"/>
                        <Binding ElementName="griddatalist" Path="ActualHeight" UpdateSourceTrigger="PropertyChanged"/>
                        <Binding ElementName="griddatalist" Path="ActualWidth" UpdateSourceTrigger="PropertyChanged"/>
                    </MultiBinding>
                </Popup.VerticalOffset>

                   VerticalOffset="-15"  >

                <Border Width="{Binding ElementName=griddatalist, Path=ActualWidth}" Height="20" Background="{StaticResource SelectedLine}">
                    <TextBlock x:Name="selectedCount" Height="20" Width="55" Margin="8,2,8,2" FontSize="12" Foreground="#FFFFFF"/>
                    <TextBlock x:Name="selectedCount" Height="20" Width="55" Margin="8,2,8,2" FontWeight="Bold" FontSize="12" Foreground="#FFFFFF"/>
                </Border>
            </Popup>

主要是这句话

<MultiBinding Converter="{StaticResource ver}">
                        <Binding ElementName="griddatalist"/>#这里绑定了控件
                        <Binding ElementName="griddatalist" Path="ActualHeight" UpdateSourceTrigger="PropertyChanged"/>
                        <Binding ElementName="griddatalist" Path="ActualWidth" UpdateSourceTrigger="PropertyChanged"/>
                    </MultiBinding>

下面是converter

public class DispatchListPopupVer : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {

            DataGrid grid = values[0] as DataGrid;

            double horizon = 0;

            double.TryParse(values[1].ToString(), out horizon);

            ScrollViewer scrollview = FindVisualChild<ScrollViewer>(grid);

            if (scrollview != null)
            {
                if (scrollview.ComputedHorizontalScrollBarVisibility== Visibility.Visible)
                {
                    return horizon - 34;
                }
                else
                {
                    return horizon - 20;
                }
            }
            else
            {
                 return horizon - 34;
            }

        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }

        private childItem FindVisualChild<childItem>(DependencyObject obj)
    where childItem : DependencyObject
        {
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
            {
                DependencyObject child = VisualTreeHelper.GetChild(obj, i);
                if (child != null && child is childItem)
                    return (childItem)child;
                else
                {
                    childItem childOfChild = FindVisualChild<childItem>(child);
                    if (childOfChild != null)
                        return childOfChild;
                }
            }
            return null;
        }
    }