GridControl.GroupRowExpanding Event

Occurs when a group row is about to be expanded, allowing cancellation of the action.

Namespace: DevExpress.Xpf.Grid

Assembly: DevExpress.Xpf.Grid.v21.2.dll


public event RowAllowEventHandler GroupRowExpanding

Event Data

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

Property Description
Allow Gets or sets whether the operation is allowed.
Handled Gets or sets a value that indicates the present state of the event handling for a routed event as it travels the route. Inherited from RoutedEventArgs.
OriginalSource Gets the original reporting source as determined by pure hit testing, before any possible Source adjustment by a parent class. Inherited from RoutedEventArgs.
RoutedEvent Gets or sets the RoutedEvent associated with this RoutedEventArgs instance. Inherited from RoutedEventArgs.
Row Gets the processed row. Inherited from RowEventArgs.
RowHandle Gets the processed row’s handle. Inherited from RowEventArgs.
Source Gets or sets a reference to the object that raised the event. Inherited from RoutedEventArgs.

The event data class exposes the following methods:

Method Description
InvokeEventHandler(Delegate, Object) When overridden in a derived class, provides a way to invoke event handlers in a type-specific way, which can increase efficiency over the base implementation. Inherited from RoutedEventArgs.
OnSetSource(Object) When overridden in a derived class, provides a notification callback entry point whenever the value of the Source property of an instance changes. Inherited from RoutedEventArgs.


The GroupRowExpanding event is raised before a group row is expanded by an end-user or in code, allowing you to cancel this action. The group row is identified by its handle via the RowEventArgs.RowHandle property. To prevent the group row from being expanded, set the event parameter’s RowAllowEventArgs.Allow parameter to false.

Group rows can be expanded recursively using the GridViewBase.ExpandFocusedRow method overload with the recursive parameter set to true. In this instance, the GroupRowExpanding event is raised only once (for the row passed as this method’s parameter). This event isn’t raised for nesting group rows.

The GridControl.ExpandAllGroups method allows you to expand all group rows. In this instance, the GroupRowExpanding event is raised only once. The event parameter’s RowEventArgs.RowHandle property returns an invalid row handle (DataControlBase.InvalidRowHandle).

After the group row has been expanded, the GridControl.GroupRowExpanded event is raised.

To learn more, see Expanding and Collapsing Group Rows.


The following example shows how to customize whether a particular group row can be expanded.In this example, the 'Status: Invalidated' group row is prevented from being expanded, and the full expanding is disabled. To do this, the GroupRowExpanding event is handled, and the event parameter's Allow property is set to false when the RowHandle property returns the 'Status: Invalidated' row's handle, or an invalid handle (this happens when all group rows are about to be expanded).

View Example

using System.Windows;
using DevExpress.Xpf.Grid;
using DXExample.DemoData;

namespace DXGrid_PreventGroupRowsFromExpanding {
    public partial class Window1 : Window {
        public Window1() {
            gridControl1.ItemsSource = Invoice.GetData();
        private void gridControl1_GroupRowExpanding(object sender, RowAllowEventArgs e) {
            if ( e.Row == null ||
                ((Invoice)e.Row).Status == InvoiceStatus.Invalidated &&
                colStatus.GroupIndex != -1 )
                e.Allow = false;
See Also