Class VirtualTreeView

The VirtualTreeView displays a hierarchical collection of expandable TreeNode items maintained by a TreeModel. A flattened representations of the hierarchy of nodes can be accessed through the VisibleNodes property of the Model where each visible node is mapped to a row index and vice versa. TreeNodesFlattenedList also implements ILineSizeHost and the VirtualTreeView assigns it to RowHeightsProvider in order to be able to pixel scroll through visible and expanded nodes.

VirtualTreeView returns cell contents with the GetRenderStyleInfo(RowColumnIndex) method which returns a TreeRenderStyleInfo object. Each cell is associated with a Syncfusion.Windows.Controls.VirtualTreeView.TreeCellRenderer object which provides methods for measuring, arranging and drawing contents of a cell. The VirtualTreeView implements the OnArrangeContent(Size) and System.Windows.UIElement.OnRender(System.Windows.Media.DrawingContext) methods. Within implementation of the OnArrangeContent method each cells UIElement children are placed on the controls area. A cell renderer can also be without any UIElement children and instead draw all its contents directly to the DrawingContext of the VirtualizingCellsControl when the System.Windows.UIElement.OnRender(System.Windows.Media.DrawingContext) method is executed. For a cell renderer it is also possible to do both: Arrange UIElements on the controls area and draw additional contents in its render area. There are also various optimization techniques that can be implemented with the renderer and are discussed in the ICellRenderer overview.

The virtualization of UIElement children of cell renderers is implemented in the arrange cells code. At the time a cell is placed the cell renderer is called to create and intialize the UIElement children. When a cell is scrolled out of view the cell renderer is called to unload the UIElement children. A cell renderer can decide whether to unload a UIElement, keep it alive or move it to a recycle bin and reuse it later. The main logic of this code is implemented by the TreeVirtualizingCellRendererBase<T> class which contains more detailed discussion about this feature.

Inheritance
System.Object
VisualContainer
ScrollControl
ScrollAxisControl
VirtualizingCellsControl
VirtualTreeView
Implements
System.Windows.Controls.Primitives.IScrollInfo
System.IDisposable
Inherited Members
Namespace: Syncfusion.Windows.Controls.VirtualTreeView
Assembly: Syncfusion.GridCommon.Wpf.dll
Syntax
public class VirtualTreeView : VirtualizingCellsControl, IScrollBarProvider, IScrollInfo, IDisposable

Constructors

VirtualTreeView()

Initializes a new instance of the VirtualTreeView class.

Declaration
public VirtualTreeView()

Fields

NodeTemplateProperty

Defines the DataTemplate to use with the expandable node renderer.

Declaration
public static readonly DependencyProperty NodeTemplateProperty
Field Value
Type Description
System.Windows.DependencyProperty

Properties

Model

Gets or sets the model.

Declaration
public TreeModel Model { get; set; }
Property Value
Type Description
TreeModel

The model.

NodeTemplate

Gets or sets the DataTemplate to use with the expandable node renderer.

Declaration
public DataTemplate NodeTemplate { get; set; }
Property Value
Type Description
System.Windows.DataTemplate

The node template.

RenderStyles

Returns a container object which manages cell styles (TreeRenderStyleInfo) of rendered cells that have been scrolled into view.

Declaration
public TreeControlRenderStyles RenderStyles { get; }
Property Value
Type Description
TreeControlRenderStyles

Methods

ArrangeCellUIElements(Size)

Arranges the cells row by row. For each cell the virtual OnArrangeCell(ArrangeCellArgs) method is called. OnArrangeCell gets the ICellRenderer for a cell and calls its Arrange(ArrangeCellArgs) method.

The method also implements the virtualization of UIElement children of cell renderers. It create new UIElement objects for cells scrolled into view or unload UIElements for cells scrolled out of view. If a UIElement has focus whenscrolled out of view it will be kept alive and not unloaded.

Declaration
protected override void ArrangeCellUIElements(Size arrangeSize)
Parameters
Type Name Description
System.Windows.Size arrangeSize
Overrides

CreateScrollAxis(Orientation, Boolean, IScrollBar, ILineSizeHost)

Creates the row or column scroll axis. The default implementation of this method creates either a PixelScrollAxis or LineScrollAxis object. You can override this method if you want to add support for another custom tailored scroll axis object.

Declaration
protected override ScrollAxisBase CreateScrollAxis(Orientation orientation, bool pixelScroll, IScrollBar scrollBar, ILineSizeHost lineSizes)
Parameters
Type Name Description
System.Windows.Controls.Orientation orientation

The orientation (Vertical for row scrolling, Horizontal for column scrolling)
System.Boolean pixelScroll

if set to true pixel scroll; otherwise line scrolling.
IScrollBar scrollBar

The state of the scroll bar.
ILineSizeHost lineSizes

An object that provides row or column sizes.
Returns
Type Description
ScrollAxisBase

The scroll axis object.
Overrides

GetCellRenderer(IRenderCellInfo)

Gets the cell renderer from a render cell style.

Declaration
protected override ICellRenderer GetCellRenderer(IRenderCellInfo cellInfo)
Parameters
Type Name Description
IRenderCellInfo cellInfo

The render cell style.
Returns
Type Description
ICellRenderer
Overrides

GetCellRenderer(DependencyObject)

Gets the CellRendererProperty attached dependency property value.

Declaration
public static TreeCellRenderer GetCellRenderer(DependencyObject dpo)
Parameters
Type Name Description
System.Windows.DependencyObject dpo

The instance to be queried for the effective value of the dependency property.
Returns
Type Description
Syncfusion.Windows.Controls.VirtualTreeView.TreeCellRenderer

Returns the effective value for the given instance.

GetRenderCellInfo(Int32, Int32)

Gets the render cell style for a cell. VirtualizingCellsControl solely relies on the IRenderCellInfo for drawing and renderer information of a cell. Concrete implementations of this interface such as GridRenderStyleInfo or TreeRenderStyleInfo can add support for additional domain specific properties.

Declaration
protected override IRenderCellInfo GetRenderCellInfo(int rowIndex, int columnIndex)
Parameters
Type Name Description
System.Int32 rowIndex

Index of the row.
System.Int32 columnIndex

Index of the column.
Returns
Type Description
IRenderCellInfo
Overrides

GetRenderStyleInfo(RowColumnIndex)

Gets the render cell style for a cell. VirtualizingCellsControl solely relies on the IRenderCellInfo for drawing and renderer information of a cell. Concrete implementations of this interface such as GridRenderStyleInfo or TreeRenderStyleInfo can add support for additional domain specific properties.

Declaration
public TreeRenderStyleInfo GetRenderStyleInfo(RowColumnIndex cellRowColumnIndex)
Parameters
Type Name Description
RowColumnIndex cellRowColumnIndex

Index of the cell row column.
Returns
Type Description
TreeRenderStyleInfo

GetRenderStyleInfo(RowColumnIndex, Boolean)

Gets the render cell style for a cell. VirtualizingCellsControl solely relies on the IRenderCellInfo for drawing and renderer information of a cell. Concrete implementations of this interface such as GridRenderStyleInfo or TreeRenderStyleInfo can add support for additional domain specific properties.

Declaration
public TreeRenderStyleInfo GetRenderStyleInfo(RowColumnIndex cellRowColumnIndex, bool createDisposableObject)
Parameters
Type Name Description
RowColumnIndex cellRowColumnIndex

Index of the cell row column.
System.Boolean createDisposableObject

if set to true create disposable object that is not cached.
Returns
Type Description
TreeRenderStyleInfo

GetRenderStyleInfo(Int32, Int32)

Gets the render cell style for a cell. VirtualizingCellsControl solely relies on the IRenderCellInfo for drawing and renderer information of a cell. Concrete implementations of this interface such as GridRenderStyleInfo or TreeRenderStyleInfo can add support for additional domain specific properties.

Declaration
public TreeRenderStyleInfo GetRenderStyleInfo(int rowIndex, int columnIndex)
Parameters
Type Name Description
System.Int32 rowIndex

Index of the row.
System.Int32 columnIndex

Index of the column.
Returns
Type Description
TreeRenderStyleInfo

GetRenderStyleInfo(Int32, Int32, Boolean)

Gets the render cell style for a cell. VirtualizingCellsControl solely relies on the IRenderCellInfo for drawing and renderer information of a cell. Concrete implementations of this interface such as GridRenderStyleInfo or TreeRenderStyleInfo can add support for additional domain specific properties.

Declaration
public TreeRenderStyleInfo GetRenderStyleInfo(int rowIndex, int columnIndex, bool createDisposableObject)
Parameters
Type Name Description
System.Int32 rowIndex

Index of the row.
System.Int32 columnIndex

Index of the column.
System.Boolean createDisposableObject

if set to true create disposable object that is not cached.
Returns
Type Description
TreeRenderStyleInfo

GetRenderStyleInfo(DependencyObject)

Gets the RenderCellInfoProperty attached dependency property value.

Declaration
public static TreeRenderStyleInfo GetRenderStyleInfo(DependencyObject dpo)
Parameters
Type Name Description
System.Windows.DependencyObject dpo

The instance to be queried for the effective value of the dependency property.
Returns
Type Description
TreeRenderStyleInfo

Returns the effective value for the given instance.

OnPrepareRenderCell(TreePrepareRenderCellEventArgs)

Raises the PrepareRenderCell event and optionally initializes the cells CellValue and CellRenderer.

Declaration
protected virtual void OnPrepareRenderCell(TreePrepareRenderCellEventArgs e)
Parameters
Type Name Description
TreePrepareRenderCellEventArgs e

The TreePrepareRenderCellEventArgs instance containing the event data.

OnPreviewMouseMove(MouseEventArgs)

Implements handling for the PreviewMouseMove�event. When no mouse button is pressed and the mouse is over a cell it calls .

Declaration
protected override void OnPreviewMouseMove(MouseEventArgs e)
Parameters
Type Name Description
System.Windows.Input.MouseEventArgs e

The System.Windows.Input.MouseEventArgs that contains the event data.
Overrides

RaiseNodeCollapsed(TreeNodeEventArgs)

Raises the NodeCollapsed event.

Declaration
public void RaiseNodeCollapsed(TreeNodeEventArgs e)
Parameters
Type Name Description
TreeNodeEventArgs e

The TreeNodeEventArgs instance containing the event data.

RaiseNodeExpanded(TreeNodeEventArgs)

Raises the NodeExpanded event.

Declaration
public void RaiseNodeExpanded(TreeNodeEventArgs e)
Parameters
Type Name Description
TreeNodeEventArgs e

The TreeNodeEventArgs instance containing the event data.

RefreshDisplay()

Refreshes the display for the tree clearing Cached Cell Styles, Recalculating Scrollbars and Repainting the whole control.

Declaration
public void RefreshDisplay()

SetCellRenderer(DependencyObject, TreeCellRenderer)

Sets the CellRendererProperty attached dependency property value.

Declaration
public static void SetCellRenderer(DependencyObject dpo, TreeCellRenderer value)
Parameters
Type Name Description
System.Windows.DependencyObject dpo

The instance to be assigned the value of the dependency property.
Syncfusion.Windows.Controls.VirtualTreeView.TreeCellRenderer value

The value.

SetRenderStyleInfo(DependencyObject, TreeRenderStyleInfo)

Sets the RenderCellInfoProperty attached dependency property value.

Declaration
public static void SetRenderStyleInfo(DependencyObject dpo, TreeRenderStyleInfo value)
Parameters
Type Name Description
System.Windows.DependencyObject dpo

The instance to be assigned the value of the dependency property.
TreeRenderStyleInfo value

The value.

Events

NodeCollapsed

Occurs when a node was collapsed.

Declaration
public event TreeNodeEventHandler NodeCollapsed
Event Type
Type Description
TreeNodeEventHandler

NodeExpanded

Occurs when node was expanded.

Declaration
public event TreeNodeEventHandler NodeExpanded
Event Type
Type Description
TreeNodeEventHandler

PrepareRenderCell

Occurs just before a cell is arranged on the display in the tree control and allows you to change the settings of the TreeRenderStyleInfo. Changes made to the style's properties will only be made for rendering the style and will not be commited back to the tree node.

Declaration
public event TreePrepareRenderCellEventHandler PrepareRenderCell
Event Type
Type Description
TreePrepareRenderCellEventHandler

Implements

System.Windows.Controls.Primitives.IScrollInfo
System.IDisposable