TreeList.VirtualTreeGetCellValue Event

This event allows you to initialize cells (and optionally the check state) of the processed node, when populating the Tree List control with data dynamically.

Namespace : DevExpress.XtraTreeList

Assembly : DevExpress.XtraTreeList.v25.2.dll

NuGet Packages : DevExpress.Win.Navigation, DevExpress.Win.TreeList

csharp

[DXCategory("VirtualTree")]
public event VirtualTreeGetCellValueEventHandler VirtualTreeGetCellValue

<DXCategory("VirtualTree")>
Public Event VirtualTreeGetCellValue As VirtualTreeGetCellValueEventHandler

Event Data

The VirtualTreeGetCellValue event's data class is VirtualTreeGetCellValueInfo. The following properties provide information specific to this event:

Property	Description
CellData	Gets or sets the current cell value (when VirtualTreeGetCellValueInfo.IsCheckState is false ) or the node’s check state (when VirtualTreeGetCellValueInfo.IsCheckState is true ).
Column	Gets the column that contains the cell currently being processed.
IsCheckState	Gets whether the TreeList.VirtualTreeGetCellValue event/ IVirtualTreeListData.VirtualTreeGetCellValue interface method is currently fired for you to provide a node’s check state.
Node	Gets an instance of the business object being currently processed.

Remarks

For more information, see Virtual Mode (Dynamic Data Loading) Using Events (Tree List Level).

Example

The following demo shows how to use the TreeList.VirtualTreeGetChildNodes and TreeList.VirtualTreeGetCellValue events to specify data for a Tree List control.

Run Demo: Explorer(Virtual Tree)

The navigationTreeList control in this demo displays directories of the file system. Instead of loading the entire directory structure on application startup, this control loads directories on demand (when a user expands a specific directory).

The TreeList.VirtualTreeGetChildNodes event is handled to dynamically load child items (directories) for a specific node. The Tree List control automatically creates nodes for all child items that the VirtualTreeGetChildNodes event handler supplies.

The TreeList.VirtualTreeGetCellValue event handler specifies values for loaded children.

C#
VB.NET

csharp

navigationTreeList.VirtualTreeGetChildNodes += OnNavigationTreeListGetChildNodes;
navigationTreeList.VirtualTreeGetCellValue += OnNavigationTreeListGetCellValue;
//...
void OnNavigationTreeListGetChildNodes(object sender, VirtualTreeGetChildNodesInfo e) {
    Cursor current = Cursor.Current;
    Cursor.Current = Cursors.WaitCursor;
    e.Children = ((Item)e.Node).GetDirectories();
    Cursor.Current = current;
}

void OnNavigationTreeListGetCellValue(object sender, VirtualTreeGetCellValueInfo e) {
    e.CellData = ((Item)e.Node).DisplayName;
}

//...
public abstract class Item : IFileImage {
    //...
    public string DisplayName {get; private set;}
    public abstract List<Item> GetDirectories();
}

AddHandler Me.navigationTreeList.VirtualTreeGetChildNodes, AddressOf Me.OnNavigationTreeListGetChildNodes
AddHandler Me.navigationTreeList.VirtualTreeGetCellValue, AddressOf Me.OnNavigationTreeListGetCellValue
'...
Private Sub OnNavigationTreeListGetChildNodes(ByVal sender As Object, ByVal e As DevExpress.XtraTreeList.VirtualTreeGetChildNodesInfo)
    Dim current As System.Windows.Forms.Cursor = System.Windows.Forms.Cursor.Current
    System.Windows.Forms.Cursor.Current = System.Windows.Forms.Cursors.WaitCursor
    e.Children = CType(e.Node, DevExpress.XtraTreeList.Demos.Item).GetDirectories()
    System.Windows.Forms.Cursor.Current = current
End Sub

Private Sub OnNavigationTreeListGetCellValue(ByVal sender As Object, ByVal e As DevExpress.XtraTreeList.VirtualTreeGetCellValueInfo)
    e.CellData = CType(e.Node, DevExpress.XtraTreeList.Demos.Item).DisplayName
End Sub

Public MustInherit Class Item
    Implements DevExpress.XtraTreeList.Demos.IFileImage
    '...
    Private _DisplayName As String, _Name As String, _FullName As String
    Public MustOverride Function GetDirectories() As List(Of DevExpress.XtraTreeList.Demos.Item)
End Class

Handle the TreeList.VirtualTreeSetCellValue event for the opposite task: if the Tree List is editable, you can write new cell values entered by users to a data source.

C#
VB.NET

csharp

using DevExpress.XtraTreeList;

void OnVirtualTreeSetCellValue(object sender, VirtualTreeSetCellValueInfo e) {
    ((Item)e.Node).DisplayName = e.NewCellData.ToString();
}

Imports DevExpress.XtraTreeList

Private Sub OnVirtualTreeSetCellValue(ByVal sender As Object, ByVal e As VirtualTreeSetCellValueInfo)
    CType(e.Node, Item).DisplayName = e.NewCellData.ToString()
End Sub

See the Explorer (Virtual Tree) demo for the complete code.

The following code snippets (auto-collected from DevExpress Examples) contain references to the VirtualTreeGetCellValue event.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#
VB.NET

winforms-spreadsheet-chart-api/CS/SpreadsheetChartAPISamples/Form1.cs#L154

csharp

treeList.VirtualTreeGetChildNodes += treeList_VirtualTreeGetChildNodes;
treeList.VirtualTreeGetCellValue += treeList_VirtualTreeGetCellValue;
#endregion

winforms-spreadsheet-pivot-table-api/CS/SpreadsheetPivotTableExamples/Form1.cs#L142

csharp

treeList.VirtualTreeGetChildNodes += treeList_VirtualTreeGetChildNodes;
treeList.VirtualTreeGetCellValue += treeList_VirtualTreeGetCellValue;
#endregion

winforms-spreadsheetcontrol-api-part-3/CS/SpreadsheetControl_API_Part03/Form1.cs#L315

csharp

treeList.VirtualTreeGetChildNodes += treeList_VirtualTreeGetChildNodes;
treeList.VirtualTreeGetCellValue += treeList_VirtualTreeGetCellValue;
#endregion

winforms-richeditcontrol-common-api/CS/RichEditAPISample/Form1.cs#L421

csharp

treeList.VirtualTreeGetChildNodes += treeList_VirtualTreeGetChildNodes;
treeList.VirtualTreeGetCellValue += treeList_VirtualTreeGetCellValue;
#endregion

winforms-richedit-document-api/CS/RichEditAPISample/Form1.cs#L409

csharp

treeList.VirtualTreeGetChildNodes += treeList_VirtualTreeGetChildNodes;
treeList.VirtualTreeGetCellValue += treeList_VirtualTreeGetCellValue;
#endregion

winforms-spreadsheet-chart-api/VB/SpreadsheetChartAPISamples/Form1.vb#L149

AddHandler treeList.VirtualTreeGetChildNodes, AddressOf treeList_VirtualTreeGetChildNodes
AddHandler treeList.VirtualTreeGetCellValue, AddressOf treeList_VirtualTreeGetCellValue
' #End Region

winforms-spreadsheet-pivot-table-api/VB/SpreadsheetPivotTableExamples/Form1.vb#L135

AddHandler treeList.VirtualTreeGetChildNodes, AddressOf treeList_VirtualTreeGetChildNodes
AddHandler treeList.VirtualTreeGetCellValue, AddressOf treeList_VirtualTreeGetCellValue
' #End Region

winforms-spreadsheetcontrol-api-part-3/VB/SpreadsheetControl_API_Part03/Form1.vb#L318

AddHandler treeList.VirtualTreeGetChildNodes, AddressOf treeList_VirtualTreeGetChildNodes
            AddHandler treeList.VirtualTreeGetCellValue, AddressOf treeList_VirtualTreeGetCellValue
#End Region

winforms-richeditcontrol-common-api/VB/RichEditAPISample/Form1.vb#L413

AddHandler treeList.VirtualTreeGetChildNodes, AddressOf treeList_VirtualTreeGetChildNodes
AddHandler treeList.VirtualTreeGetCellValue, AddressOf treeList_VirtualTreeGetCellValue
' #End Region

winforms-richedit-document-api/VB/RichEditAPISample/Form1.vb#L414

AddHandler treeList.VirtualTreeGetChildNodes, AddressOf treeList_VirtualTreeGetChildNodes
            AddHandler treeList.VirtualTreeGetCellValue, AddressOf treeList_VirtualTreeGetCellValue
#End Region

TreeList.VirtualTreeGetCellValue Event

TreeList.VirtualTreeGetCellValue Event

Declaration

Event Data

Remarks

Example

Related GitHub Examples