DxTreeView.BeforeCollapse Event

Fires when a node is about to be collapsed and allows you to cancel the action.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v23.2.dll

NuGet Package: DevExpress.Blazor

Declaration

[Parameter]
public Action<TreeViewNodeCancelEventArgs> BeforeCollapse { get; set; }

Event Data

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

Property	Description
Cancel	Specifies whether the action that raised the event should be canceled.
CausedByAPI	Obsolete. Specifies whether an event was triggered by a user action or programmatically. Inherited from TreeViewNodeEventArgs.
NodeInfo	Returns information about a node related to the event. Inherited from TreeViewNodeEventArgs.
Reason	Returns the reason why the TreeView node’s state changes. Inherited from TreeViewNodeEventArgs.

Remarks

The code sample below demonstrates how to prohibit root-level nodes from collapsing.

<DxTreeView BeforeCollapse="@BeforeCollapse">
    ...
</DxTreeView>

@code  {
    void BeforeCollapse(TreeViewNodeCancelEventArgs e) {
        if (e.NodeInfo.Level == 0) e.Cancel = true; 
    }
}