McBasic™ 0.7.881 · Build 881 · 12 min read

Controls · Visual control

TreeView

Select nodes, insert a child and complete a lazy expansion request.

48 properties26 events1 methodsDefault: Change

Build the TreeView lesson Properties Events Methods

Use it in a Form#

TreeNodes.Item uses one-based collection positions. Lazy expansion has an identity: copy RequestedId to CompletionId before supplying LazyChildren. Using only a row index would risk filling a different request after the visible tree changes.

Add TreeView to its intended parent and name it tvwTree for this example:

Property	Example value
`Items`	`"Root\n Child 1\n Child 2\nOther"`
`SelectedIndex`	`1`
`ExpandAll`	`True`

A complete handler from Forms/frmMain.bas. The linked lesson includes its surrounding controls, declarations and helpers.

Forms/frmMain.bas

Private Sub tvwTree_Change()
    If tvwTree.SelectedNode Is Nothing Then
        lblStatus.Caption = "No selected node"
    Else
        lblStatus.Caption = "Selected node: " & tvwTree.SelectedNode.Text
    End If
End Sub

Properties#

Contract defaults are shown below. Where a new control has a different Designer starting value, that value is listed separately.

`Left`

DoubleDefault: 0

Horizontal position in device-independent points, relative to the parent container.

Range: -100000 to 100000.

`Top`

DoubleDefault: 0

Vertical position in device-independent points, relative to the parent container.

Range: -100000 to 100000.

`Width`

DoubleDefault: 220

Control width in device-independent points.

Range: 0 to 100000.

`Height`

DoubleDefault: 140

Control height in device-independent points.

Range: 0 to 100000.

`MinWidth`

DoubleDefault: 0

Minimum control width in device-independent points; 0 lets the parent layout choose.

Range: 0 to 100000.

`MinHeight`

DoubleDefault: 0

Minimum control height in device-independent points; 0 lets the parent layout choose.

Range: 0 to 100000.

`MaxWidth`

DoubleDefault: 100000

Maximum control width in device-independent points.

Range: 0 to 100000.

`MaxHeight`

DoubleDefault: 100000

Maximum control height in device-independent points.

Range: 0 to 100000.

`Font`

StringDefault: ""

Node font as Family|Size or Family|Size|Regular/Bold|Normal/Italic, size 6–96 DIP. Empty uses the theme font.

`ForeColor`

StringDefault: ""

Node text color as #RRGGBB. Empty inherits the Form color or theme.

`BackColor`

StringDefault: ""

Tree surface color as #RRGGBB. Empty uses the theme background.

`Padding`

StringDefault: "4"

Internal spacing around TreeView nodes as one non-negative DIP value or Left,Top,Right,Bottom.

`BorderStyle`

StringDefault: "Solid"

TreeView border rendering: Solid or None.

`BorderColor`

StringDefault: ""

Border color as #RRGGBB. Empty uses the theme border color.

`BorderWidth`

DoubleDefault: 1

Uniform border width in device-independent points.

Range: 0 to 100.

`CornerRadius`

DoubleDefault: 0

Uniform TreeView corner radius in device-independent points.

Range: 0 to 1000.

`HorizontalScrollBar`

StringDefault: "Auto"

Horizontal scrollbar visibility: Auto, Visible, Hidden or Disabled.

`VerticalScrollBar`

StringDefault: "Auto"

Vertical scrollbar visibility: Auto, Visible, Hidden or Disabled.

`HideSelection`

BooleanDefault: True

Hides the selected-row presentation when keyboard focus leaves the TreeView without clearing SelectedNode.

`ShowLines`

BooleanDefault: True

Draws connector lines between visible parent and child nodes.

`ShowRootLines`

BooleanDefault: True

Draws the root-level connector trunk when ShowLines is enabled.

`ShowExpanders`

BooleanDefault: True

Shows the expand/collapse chevron for nodes that have children; keyboard and double-click expansion remain available when hidden.

`FullRowSelect`

BooleanDefault: False

Extends the selection surface across the available TreeView row instead of only the node content.

`AccessibleName`

StringDefault: ""

Name announced by assistive technology. Empty uses the stable control Name.

`AccessibleDescription`

StringDefault: ""

Additional help text announced by assistive technology.

`AutomationId`

StringDefault: ""

Stable automation identifier; empty uses the component Name.

`AccessibleRole`

StringDefault: "Auto"

Accessibility role override. Auto preserves the native semantic role; explicit values use the corresponding platform automation role.

`ToolTipText`

StringDefault: ""

Help text shown when the pointer rests over the running control; empty disables the tooltip.

`Tag`

StringDefault: ""

Application-defined text associated with this control; McBasic™ does not interpret it.

`TabIndex`

LongDefault: 0

Keyboard navigation order within the parent container; lower values come first.

Range: 0 to 100000.

`TabStop`

BooleanDefault: True

Whether Tab navigation can move focus to this TreeView.

`ZIndex`

LongDefault: 0

Stacking order among sibling controls; larger values appear in front. Equal values preserve document order.

Range: -100000 to 100000.

`Anchor`

StringDefault: "Left,Top"Not in InspectorNot serialized

Edges kept at their authored distance when the parent resizes. Use a comma-separated combination of Left, Top, Right and Bottom; Dock overrides the effective anchor without deleting it.

`Dock`

StringDefault: "None"

Automatic placement within the parent: None, Left, Top, Right, Bottom or Fill. Dock overrides effective Anchor layout without deleting the stored anchors.

`Margin`

StringDefault: "0"

External spacing as one non-negative DIP value or Left,Top,Right,Bottom.

`Cursor`

StringDefault: "Default"

Pointer shown over the control: Default, Arrow, Hand, IBeam, Cross, Wait, Help, SizeAll, SizeNS, SizeWE, SizeNWSE, SizeNESW or NotAllowed.

`Opacity`

DoubleDefault: 1

Visual opacity from 0 (transparent) to 1 (opaque).

Range: 0 to 1.

`DesignLocked`

BooleanDefault: FalseDesigner only

Prevents movement and resizing in the Designer without changing runtime interaction.

`Visible`

BooleanDefault: True

Whether the control is shown in the running application.

`Enabled`

BooleanDefault: True

Whether the control accepts user interaction in the running application.

`HitTestVisible`

BooleanDefault: True

Whether the running control participates in pointer hit testing. The control remains selectable in the Designer.

`AllowDrop`

BooleanDefault: False

Whether this running control accepts application drag-and-drop operations; Designer movement is separate.

`DragMode`

LongDefault: 0

VB control drag: 0 Manual (code starts a drag with the Drag method) or 1 Automatic (a left-button press starts a drag, and the control raises no Click, MouseDown or MouseUp for that press).

Range: 0 to 1.

`DragIcon`

StringDefault: ""

Case-insensitive name of a declared project image resource shown under the pointer while this control is dragged; empty shows a grey outline of the control.

`Items`

StringDefault: "Root\n Child 1\n Child 2\nOther"

One node per line. Two leading spaces increase the node depth by one; nodes may be selected and expanded at runtime.

`SelectedIndex`

LongDefault: 0

Zero-based depth-first node index; -1 means no node is selected.

Range: -1 to 100000.

`ExpandAll`

BooleanDefault: True

Whether all nodes are expanded when the control is configured or this property changes.

`Index`

LongDefault: -1Read only in BASICDesigner Index row

Position of this control in its control array, 0 to 32767. Several controls share one name only when every one of them has an Index. Absent from the layout, and -1 in code, when the control is not in an array.

Designer values: 0 to 32767. Clear the dedicated Index row for a non-array control; BASIC then reads -1.

Events and parameters#

Replace control with the object’s Name when creating a handler. ByRef arguments may be changed by your handler; ByVal arguments report an input value.