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.v18.2.dll

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 ASPxTreeView.ExpandedChanging event handler. The event handler prevents collapsing nodes if it has selected children in any generation.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-prevent-parent-node-collapsing-e2439

Default.aspx.cs

using DevExpress.Web.ASPxTreeView;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    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 (C#)

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

Default.aspx (VB.NET)

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

Default.aspx.vb

Imports DevExpress.Web.ASPxTreeView

Partial Public Class _Default
    Inherits System.Web.UI.Page
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    End Sub
    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
End Class