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.v23.2.dll
NuGet Packages: DevExpress.Win.Navigation, DevExpress.Win.TreeList
Declaration
[DXCategory("VirtualTree")]
public event VirtualTreeGetCellValueEventHandler VirtualTreeGetCellValueEvent 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.
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.
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();
}
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.
using DevExpress.XtraTreeList;
void OnVirtualTreeSetCellValue(object sender, VirtualTreeSetCellValueInfo e) {
((Item)e.Node).DisplayName = e.NewCellData.ToString();
}
See the Explorer (Virtual Tree) demo for the complete code.
Related GitHub Examples
The following code snippets (auto-collected from DevExpress Examples) contain references to the VirtualTreeGetCellValue event.
Note
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