// 获取要定位之前 ScrollViewer 目前的滚动位置
 var currentScrollPosition = ScrollViewer.VerticalOffset;
 var point = new Point(0, currentScrollPosition);

 // 计算出目标位置并滚动
 var targetPosition = TargetControl.TransformToVisual(ScrollViewer).Transform(point);
 ScrollViewer.ScrollToVerticalOffset(targetPosition.Y);

namespace ScrollTest
{
 /// <summary>
 /// 在 ScrollViewer 中定位到指定的控件
 /// 说明：目前支持的是垂直滚动
 /// </summary>
 public class ScrollToControlAction : TriggerAction<FrameworkElement>
 {
 public static readonly DependencyProperty ScrollViewerProperty =
 DependencyProperty.Register("ScrollViewer", typeof(ScrollViewer), typeof(ScrollToControlAction), new PropertyMetadata(null));

 public static readonly DependencyProperty TargetControlProperty =
 DependencyProperty.Register("TargetControl", typeof(FrameworkElement), typeof(ScrollToControlAction), new PropertyMetadata(null));

 /// <summary>
 /// 目标 ScrollViewer
 /// </summary>
 public ScrollViewer ScrollViewer
 {
 get { return (ScrollViewer)GetValue(ScrollViewerProperty); }
 set { SetValue(ScrollViewerProperty, value); }
 }

 /// <summary>
 /// 要定位的到的控件
 /// </summary>
 public FrameworkElement TargetControl
 {
 get { return (FrameworkElement)GetValue(TargetControlProperty); }
 set { SetValue(TargetControlProperty, value); }
 }

 protected override void Invoke(object parameter)
 {
 if (TargetControl == null || ScrollViewer == null)
 {
 throw new ArgumentNullException($"{ScrollViewer} or {TargetControl} cannot be null");
 }

 // 检查指定的控件是否在指定的 ScrollViewer 中
 // TODO: 这里只是指定离它最近的 ScrollViewer，并没有继续向上找
 var container = TargetControl.FindParent<ScrollViewer>();
 if (container == null || container != ScrollViewer)
 {
 throw new Exception("The TargetControl is not in the target ScrollViewer");
 }

 // 获取要定位之前 ScrollViewer 目前的滚动位置
 var currentScrollPosition = ScrollViewer.VerticalOffset;
 var point = new Point(0, currentScrollPosition);

 // 计算出目标位置并滚动
 var targetPosition = TargetControl.TransformToVisual(ScrollViewer).Transform(point);
 ScrollViewer.ScrollToVerticalOffset(targetPosition.Y);
 }
 }
}

<Button>
 <i:Interaction.Triggers>
  <i:EventTrigger EventName="Click">
  <local:ScrollToControlAction ScrollViewer="{Binding ElementName=s}" TargetControl="{Binding ElementName=txtSectionC}" />
  </i:EventTrigger>
 </i:Interaction.Triggers>
</Button>