wpf-devexpress-dot-xpf-dot-grid-dot-gridcontrol-d88b5980.md
Occurs when a group row is about to be collapsed, allowing cancellation of the action.
Namespace : DevExpress.Xpf.Grid
Assembly : DevExpress.Xpf.Grid.v25.2.dll
NuGet Package : DevExpress.Wpf.Grid.Core
public event RowAllowEventHandler GroupRowCollapsing
Public Event GroupRowCollapsing As RowAllowEventHandler
The GroupRowCollapsing 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 GroupRowCollapsing event is raised before a group row is collapsed 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 collapsed, set the event parameter’s RowAllowEventArgs.Allow parameter to false.
Group rows can be collapsed recursively using the GridViewBase.CollapseFocusedRow method overload with the recursive parameter set to true. In this instance, the GroupRowCollapsing 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.CollapseAllGroups method allows you to collapse all group rows. In this instance, the GroupRowCollapsing 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 collapsed, the GridControl.GroupRowCollapsed event is raised.
To learn more, see Expanding and Collapsing Group Rows.
The following example does not allow users to collapse the Status: Invalidated group row and expand the Status: Delivered group row.
View Example: Forbid Expand and Collapse Operations for Group Rows
<dxg:GridControl x:Name="grid"
EndGrouping="OnEndGrouping"
GroupRowCollapsing="OnGroupRowCollapsing"
GroupRowCollapsed="OnGroupRowCollapsed"
GroupRowExpanding="OnGroupRowExpanding"
GroupRowExpanded="OnGroupRowExpanded">
<dxg:GridColumn FieldName="ProductName"/>
<dxg:GridColumn FieldName="Price"/>
<dxg:GridColumn FieldName="Discount"/>
<dxg:GridColumn FieldName="Status" GroupIndex="0" SortOrder="Descending"/>
<dxg:GridControl.View>
<dxg:TableView x:Name="view" GroupValueTemplateSelector="{StaticResource groupRowTemplateSelector}"/>
</dxg:GridControl.View>
</dxg:GridControl>
void OnEndGrouping(object sender, RoutedEventArgs e) {
if (grid.Columns[nameof(Invoice.Status)].GroupIndex == 0) {
var childRow = grid.FindRowByValue(grid.Columns[nameof(Invoice.Status)], InvoiceStatus.Invalidated);
var groupRow = grid.GetParentRowHandle(childRow);
grid.ExpandGroupRow(groupRow);
childRow = grid.FindRowByValue(grid.Columns[nameof(Invoice.Status)], InvoiceStatus.Delivered);
groupRow = grid.GetParentRowHandle(childRow);
grid.CollapseGroupRow(groupRow);
}
}
void OnGroupRowCollapsing(object sender, RowAllowEventArgs e) {
if (e.Row != null && grid.GetGroupRowValue(e.RowHandle).Equals(InvoiceStatus.Invalidated))
e.Allow = false;
}
void OnGroupRowCollapsed(object sender, RowEventArgs e) {
if (e.Row == null && grid.Columns[nameof(Invoice.Status)].GroupIndex == 0) {
var childRow = grid.FindRowByValue(grid.Columns[nameof(Invoice.Status)], InvoiceStatus.Invalidated);
var groupRow = grid.GetParentRowHandle(childRow);
grid.ExpandGroupRow(groupRow);
}
}
void OnGroupRowExpanding(object sender, RowAllowEventArgs e) {
if (e.Row != null && grid.GetGroupRowValue(e.RowHandle).Equals(InvoiceStatus.Delivered))
e.Allow = false;
}
void OnGroupRowExpanded(object sender, RowEventArgs e) {
if (e.Row == null && grid.Columns[nameof(Invoice.Status)].GroupIndex == 0) {
var childRow = grid.FindRowByValue(grid.Columns[nameof(Invoice.Status)], InvoiceStatus.Delivered);
var groupRow = grid.GetParentRowHandle(childRow);
grid.CollapseGroupRow(groupRow);
}
}
Private Sub OnEndGrouping(ByVal sender As Object, ByVal e As RoutedEventArgs)
If Me.grid.Columns(NameOf(Invoice.Status)).GroupIndex = 0 Then
Dim childRow = Me.grid.FindRowByValue(Me.grid.Columns(NameOf(Invoice.Status)), InvoiceStatus.Invalidated)
Dim groupRow = Me.grid.GetParentRowHandle(childRow)
Me.grid.ExpandGroupRow(groupRow)
childRow = Me.grid.FindRowByValue(Me.grid.Columns(NameOf(Invoice.Status)), InvoiceStatus.Delivered)
groupRow = Me.grid.GetParentRowHandle(childRow)
Me.grid.CollapseGroupRow(groupRow)
End If
End Sub
Private Sub OnGroupRowCollapsing(ByVal sender As Object, ByVal e As RowAllowEventArgs)
If e.Row IsNot Nothing AndAlso Me.grid.GetGroupRowValue(e.RowHandle).Equals(InvoiceStatus.Invalidated) Then e.Allow = False
End Sub
Private Sub OnGroupRowCollapsed(ByVal sender As Object, ByVal e As RowEventArgs)
If e.Row Is Nothing AndAlso Me.grid.Columns(NameOf(Invoice.Status)).GroupIndex = 0 Then
Dim childRow = Me.grid.FindRowByValue(Me.grid.Columns(NameOf(Invoice.Status)), InvoiceStatus.Invalidated)
Dim groupRow = Me.grid.GetParentRowHandle(childRow)
Me.grid.ExpandGroupRow(groupRow)
End If
End Sub
Private Sub OnGroupRowExpanding(ByVal sender As Object, ByVal e As RowAllowEventArgs)
If e.Row IsNot Nothing AndAlso Me.grid.GetGroupRowValue(e.RowHandle).Equals(InvoiceStatus.Delivered) Then e.Allow = False
End Sub
Private Sub OnGroupRowExpanded(ByVal sender As Object, ByVal e As RowEventArgs)
If e.Row Is Nothing AndAlso Me.grid.Columns(NameOf(Invoice.Status)).GroupIndex = 0 Then
Dim childRow = Me.grid.FindRowByValue(Me.grid.Columns(NameOf(Invoice.Status)), InvoiceStatus.Delivered)
Dim groupRow = Me.grid.GetParentRowHandle(childRow)
Me.grid.CollapseGroupRow(groupRow)
End If
End Sub
The following code snippet (auto-collected from DevExpress Examples) contains a reference to the GroupRowCollapsing 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.
EndGrouping="OnEndGrouping"
GroupRowCollapsing="OnGroupRowCollapsing"
GroupRowCollapsed="OnGroupRowCollapsed"
#ExternalSource("..\..\MainWindow.xaml",20)
AddHandler Me.grid.GroupRowCollapsing, New DevExpress.Xpf.Grid.RowAllowEventHandler(AddressOf Me.OnGroupRowCollapsing)
See Also