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ASPxClientTreeList.StartDragNode Event

Occurs before a node is dragged by an end-user.

Declaration

StartDragNode: ASPxClientEvent<ASPxClientTreeListStartDragNodeEventHandler<ASPxClientTreeList>>

Event Data

The StartDragNode event handler receives an argument of the ASPxClientTreeListStartDragNodeEventArgs type. The following properties provide information specific to this event.

Property Description
cancel Gets or sets a value indicating whether the action which raised the event should be canceled.
htmlEvent Provides access to the parameters associated with the ASPxClientTreeList.NodeClick and ASPxClientTreeList.NodeDblClick events.
nodeKey Gets the processed node's key value.
targets Gets an array of targets where a node can be dragged.

Remarks

The StartDragNode event is raised after an end-user has clicked a node, and allows you to:

End-users are allowed to move nodes if the TreeListSettingsEditing.AllowNodeDragDrop option is enabled.

To learn more, see Drag and Drop.

Examples

This example demonstrates how to implement node dragging outside the ASPxTreeList. The ASPxClientTreeList.StartDragNode client event is handled to add the cart image to the list of target elements, so that an end-user can drag nodes to the cart. If a node has been dropped to the cart, the cart image changes (in the ASPxClientTreeList.EndDragNode client event handler) and the node is painted red (using the server ASPxTreeList.HtmlRowPrepared event).

The image below shows the result:

cdDragDropOutside

<dx:ASPxImage id="ASPxImage1" runat="server" ImageUrl="~/Images/cart-empty.png" ClientInstanceName="imageCart" >
</dx:ASPxImage>

<dx:ASPxTreeList ID="ASPxTreeList1" runat="server" AutoGenerateColumns="False" ClientInstanceName="treeList"
    DataSourceID="AccessDataSource1" KeyFieldName="ProductID" ParentFieldName="ParentID" 
    OnCustomCallback="ASPxTreeList1_CustomCallback" OnHtmlRowPrepared="ASPxTreeList1_HtmlRowPrepared">
    <Columns>
        <dx:TreeListTextColumn FieldName="ProductName" VisibleIndex="1">
        </dx:TreeListTextColumn>
        <dx:TreeListTextColumn FieldName="UnitPrice" VisibleIndex="2">
            <PropertiesTextEdit DisplayFormatString="c2">
            </PropertiesTextEdit>
        </dx:TreeListTextColumn>
    </Columns>
        <SettingsEditing AllowNodeDragDrop="True" />
    <ClientSideEvents 
        EndDragNode="function(s, e) {
            if(e.targetElement == imageCart.GetMainElement()) {
                imageCart.SetImageUrl('Images/cart-filled.png');
                e.cancel = true;
                s.PerformCustomCallback(e.nodeKey);
            }
        }" 
        StartDragNode="function(s, e) {
            if(s.GetNodeState(e.nodeKey) == 'Child')
                e.targets.push(imageCart.GetMainElement());
        }" />
</dx:ASPxTreeList>
using System.Collections;
using DevExpress.Web.ASPxEditors;
using DevExpress.Web.ASPxTreeList;

protected void Page_Load(object sender, EventArgs e){
    if (!IsPostBack && !IsCallback)
        Session["ItemsInCart"] = new ArrayList();
}

protected void ASPxTreeList1_CustomCallback(object sender, DevExpress.Web.ASPxTreeList.TreeListCustomCallbackEventArgs e){
    (Session["ItemsInCart"] as ArrayList).Add(e.Argument);
}

protected void ASPxTreeList1_HtmlRowPrepared(object sender, DevExpress.Web.ASPxTreeList.TreeListHtmlRowEventArgs e){
    ArrayList orders = Session["ItemsInCart"] as ArrayList;
    if (orders.Count == 0) return;
    if (orders.Contains(e.NodeKey))
        e.Row.ForeColor = System.Drawing.Color.OrangeRed;
}
See Also