TreeViewNodeCancelEventArgs.Cancel Property

Gets or sets a value indicating whether the action that raised the event should be canceled.

Namespace: DevExpress.Web

Assembly: DevExpress.Web.v23.2.dll

NuGet Package: DevExpress.Web

Declaration

C#

public bool Cancel { get; set; }

VB.NET

Public Property Cancel As Boolean

Property Value

Type	Description
Boolean	true if the action that raised the event should be canceled; otherwise, false.

Remarks

The TreeViewNodeCancelEventArgs object is passed to the events that fire before specific actions. The Cancel property of this object enables you to cancel the action which is about to be performed. Set this property to true to cancel the action that raised the event. This can be used if you want to prohibit performing the corresponding action with respect to specific conditions.

Example

The sample code below represents an ExpandedChanging event handler. The event handler prevents collapsing nodes if it has selected children in any generation.

Default.aspx

<dx:ASPxTreeView ID="ASPxTreeView1" runat="server" DataSourceID="XmlDataSource1" AutoPostBack="True" 
    AllowSelectNode="True" OnExpandedChanging="ASPxTreeView1_ExpandedChanging" />
<asp:XmlDataSource ID="XmlDataSource1" runat="server" DataFile="~/App_Data/MenuTabbedMenu.xml"
    XPath="/mainmenu/item"></asp:XmlDataSource>

Default.aspx.cs

protected void ASPxTreeView1_ExpandedChanging(object source, DevExpress.Web.ASPxTreeView.TreeViewNodeCancelEventArgs e) {
    if ((e.Node.Expanded) && (ASPxTreeView1.SelectedNode != null)) {
        TreeViewNode  node = ASPxTreeView1.SelectedNode.Parent;
        while (node != null) {
            if (e.Node == node) {
                e.Cancel = true;
                break;
            }
            node = node.Parent;
        }
    }
}

Default.aspx.vb

Protected Sub ASPxTreeView1_ExpandedChanging(ByVal source As Object, ByVal e As DevExpress.Web.ASPxTreeView.TreeViewNodeCancelEventArgs)
    e.Node.Expanded = True
    If e.Node.Expanded AndAlso (ASPxTreeView1.SelectedNode IsNot Nothing) Then
        Dim node As TreeViewNode = ASPxTreeView1.SelectedNode.Parent
        Do While node IsNot Nothing
            If e.Node Is node Then
                e.Cancel = True
                Exit Do
            End If
            node = node.Parent
        Loop
    End If
End Sub