Microsoft.Silverlight.Testing.Controls.TreeViewItem.HandleScrollByPage C# (CSharp) Метод

        internal bool HandleScrollByPage(bool up, ScrollViewer scrollHost, double viewportHeight, double top, double bottom, out double currentDelta)
        {
            double closeEdge = 0;
            currentDelta = CalculateDelta(up, this, scrollHost, top, bottom, out closeEdge);
            if (NumericExtensions.IsGreaterThan(closeEdge, viewportHeight))
            {
                // The item doesn't fit in the view
                return false;
            }
            if (NumericExtensions.IsLessThanOrClose(currentDelta, viewportHeight))
            {
                // The item and its children fit, but don't focus because there
                // might be more than fit
                return false;
            }
            else
            {
                // The item is partially in the view

                // Check if the header is in the view
                bool headerInView = false;
                FrameworkElement header = HeaderElement;
                if (header != null)
                {
                    double edge;
                    double delta = CalculateDelta(up, header, scrollHost, top, bottom, out edge);
                    if (NumericExtensions.IsLessThanOrClose(delta, viewportHeight))
                    {
                        headerInView = true;
                    }
                }

                TreeViewItem selected = null;
                int count = Items.Count;
                bool skip = up && ContainsSelection;
                for (int index = (up ? count - 1 : 0); 0 <= index && index < count; index += (up ? -1 : 1))
                {
                    TreeViewItem item = ItemContainerGenerator.ContainerFromIndex(index) as TreeViewItem;
                    if (item != null && item.IsEnabled)
                    {
                        if (skip)
                        {
                            if (item.IsSelected)
                            {
                                skip = false;
                                continue;
                            }
                            else if (item.ContainsSelection)
                            {
                                skip = false;
                            }
                            else
                            {
                                continue;
                            }
                        }

                        double delta;
                        if (item.HandleScrollByPage(up, scrollHost, viewportHeight, top, bottom, out delta))
                        {
                            // This item or one of its children was focused
                            return true;
                        }
                        else if (NumericExtensions.IsGreaterThan(delta, viewportHeight))
                        {
                            // The item does not fit
                            break;
                        }
                        else
                        {
                            // The item fits, but continue searching
                            selected = item;
                        }
                    }
                }

                if (selected != null)
                {
                    if (up)
                    {
                        return selected.Focus();
                    }
                    else
                    {
                        return selected.FocusInto();
                    }
                }
                else if (headerInView)
                {
                    // If none of the children fit but the header is in view,
                    // then we'll select this TreeViewItem.
                    return Focus();
                }
            }

            return false;
        }