System.Windows.Controls.ItemsControlHelper.ScrollIntoView C# (CSharp) Method

        internal void ScrollIntoView(FrameworkElement element)
        {
            // Get the ScrollHost
            ScrollViewer scrollHost = ScrollHost;
            if (scrollHost == null)
            {
                return;
            }

            // Get the position of the element relative to the ScrollHost
            GeneralTransform transform = null;
            try
            {
                transform = element.TransformToVisual(scrollHost);
            }
            catch (ArgumentException)
            {
                // Ignore failures when not in the visual tree
                return;
            }
            Rect itemRect = new Rect(
                transform.Transform(new Point()),
                transform.Transform(new Point(element.ActualWidth, element.ActualHeight)));

            // Scroll vertically
            double verticalOffset = scrollHost.VerticalOffset;
            double verticalDelta = 0;
            double hostBottom = scrollHost.ViewportHeight;
            double itemBottom = itemRect.Bottom;
            if (hostBottom < itemBottom)
            {
                verticalDelta = itemBottom - hostBottom;
                verticalOffset += verticalDelta;
            }
            double itemTop = itemRect.Top;
            if (itemTop - verticalDelta < 0)
            {
                verticalOffset -= verticalDelta - itemTop;
            }
            scrollHost.ScrollToVerticalOffset(verticalOffset);

            // Scroll horizontally
            double horizontalOffset = scrollHost.HorizontalOffset;
            double horizontalDelta = 0;
            double hostRight = scrollHost.ViewportWidth;
            double itemRight = itemRect.Right;
            if (hostRight < itemRight)
            {
                horizontalDelta = itemRight - hostRight;
                horizontalOffset += horizontalDelta;
            }
            double itemLeft = itemRect.Left;
            if (itemLeft - horizontalDelta < 0)
            {
                horizontalOffset -= horizontalDelta - itemLeft;
            }
            scrollHost.ScrollToHorizontalOffset(horizontalOffset);
        }
    }

        /// <summary>
        /// Change whether a TreeViewItem is selected.
        /// </summary>
        /// <param name="itemOrContainer">
        /// Item whose selection is changing.
        /// </param>
        /// <param name="container">
        /// Container of the item whose selection is changing.
        /// </param>
        /// <param name="selected">
        /// A value indicating whether the TreeViewItem is selected.
        /// </param>
        internal void ChangeSelection(object itemOrContainer, TreeViewItem container, bool selected)
        {
            // Ignore any change notifications if we're alread in the middle of
            // changing the selection
            if (IsSelectionChangeActive)
            {
                return;
            }

            object       oldValue = null;
            object       newValue = null;
            bool         raiseSelectionChanged = false;
            TreeViewItem element = SelectedContainer;

            // Start changing the selection
            IsSelectionChangeActive = true;
            try
            {
                if (selected && container != SelectedContainer)
                {
                    // Unselect the old value
                    oldValue = SelectedItem;
                    if (SelectedContainer != null)
                    {
                        SelectedContainer.IsSelected = false;
                        SelectedContainer.UpdateContainsSelection(false);
                    }

                    // Select the new value
                    newValue          = itemOrContainer;
                    SelectedContainer = container;
                    SelectedContainer.UpdateContainsSelection(true);
                    SelectedItem = itemOrContainer;
                    UpdateSelectedValue(itemOrContainer);
                    raiseSelectionChanged = true;

                    // Scroll the selected item into view.  We only want to
                    // scroll the header into view, if possible, because an
                    // expanded TreeViewItem contains all of its child items
                    // as well.
                    ItemsControlHelper.ScrollIntoView(container.HeaderElement ?? container);
                }
                else if (!selected && container == SelectedContainer)
                {
                    // Unselect the old value
                    SelectedContainer.UpdateContainsSelection(false);
                    SelectedContainer     = null;
                    SelectedItem          = null;
                    SelectedValue         = null;
                    oldValue              = itemOrContainer;
                    raiseSelectionChanged = true;
                }

                container.IsSelected = selected;
            }
            finally
            {
                // Finish changing the selection
                IsSelectionChangeActive = false;
            }

            // Notify when the selection changes
            if (raiseSelectionChanged)
            {
                if (SelectedContainer != null && AutomationPeer.ListenerExists(AutomationEvents.SelectionItemPatternOnElementSelected))
                {
                    AutomationPeer peer = FrameworkElementAutomationPeer.CreatePeerForElement(SelectedContainer);
                    if (peer != null)
                    {
                        peer.RaiseAutomationEvent(AutomationEvents.SelectionItemPatternOnElementSelected);
                    }
                }
                if (element != null && AutomationPeer.ListenerExists(AutomationEvents.SelectionItemPatternOnElementRemovedFromSelection))
                {
                    AutomationPeer peer = FrameworkElementAutomationPeer.CreatePeerForElement(element);
                    if (peer != null)
                    {
                        peer.RaiseAutomationEvent(AutomationEvents.SelectionItemPatternOnElementRemovedFromSelection);
                    }
                }

                OnSelectedItemChanged(new RoutedPropertyChangedEventArgs <object>(oldValue, newValue));
            }
        }