关于scrollview控件赋值没有立即响应的问题~在线等待~

<Window x:Class="test5.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        xmlns:local="clr-namespace:test5"

        Title="MainWindow" Height="573" Width="602">

    <Grid>

            <Button Click="GoToLake" Margin="207,34,210,380">Go to Lake</Button>

            <ScrollViewer Name="sv1" Width="370" Height="300" HorizontalScrollBarVisibility="Visible" VerticalScrollBarVisibility="Visible" Margin="84,186,196,48">

                <TextBlock Width="800"  Name="mapframe" ScrollViewer.CanContentScroll="True">

                    sadafafdffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffsa

                     sadafafdffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffsa

            </TextBlock>

            </ScrollViewer>

    </Grid>

</Window>

 private void GoToLake(object sender, RoutedEventArgs e)

        {

            sv1.ScrollToHorizontalOffset(440);

            double wid1 = sv1.ViewportWidth;

            double wid2 = sv1.ScrollableWidth;

            double wid3 = sv1.HorizontalOffset;

            double wid4 = sv1.ExtentWidth;

            double wid5 = sv1.ContentHorizontalOffset;

        }

我是在探究Scrollview控件的几个属性值，但是发现了一个问题~我在调试中：

会发现虽然前面，sv1.ScrollToHorizontalOffset(440);已经移动了，但是wid3 ，wid5 并没有发现这种改变，他们的值还是0，这是什么原因？ wpf scrollview --------------------编程问答-------------------- 求给力~大仙们快来~

补充：.NET技术 ,  组件/控件开发