How to: Validate Nodes (Server-Side)

• Dec 17, 2020

This example demonstrates how to check the validity of data entered by end-users into a node. Validation is implemented within the ASPxTreeList.NodeValidating event handler. In this sample, validation fails in the cases listed below:

• the department isn’t specified;
• the budget is negative.

The image below shows the result:

C#

protected void ASPxTreeList1_NodeValidating(object sender, TreeListNodeValidationEventArgs e) {
    if ((int)e.NewValues["Budget"] < 0)
        e.Errors["Budget"] = "Negative values aren't allowed";
    if (e.NewValues["Department"] == null)
        e.Errors["Department"] = "Required field";
    if (e.Errors.Count != 0)
        e.NodeError = "Node update failed. Please check node values.";
}

JS

<dxwtl:ASPxTreeList ID="ASPxTreeList1" runat="server" AutoGenerateColumns="False"
    DataSourceID="AccessDataSource1"
    KeyFieldName="ID" ParentFieldName="ParentID" OnNodeValidating="ASPxTreeList1_NodeValidating">
    <Columns>
        <dxwtl:TreeListTextColumn FieldName="Department" VisibleIndex="0">
        </dxwtl:TreeListTextColumn>
        <dxwtl:TreeListTextColumn FieldName="Budget" VisibleIndex="1">
        </dxwtl:TreeListTextColumn>
        <dxwtl:TreeListTextColumn FieldName="Location" VisibleIndex="2">
        </dxwtl:TreeListTextColumn>
        <dxwtl:TreeListTextColumn FieldName="Phone" VisibleIndex="3">
        </dxwtl:TreeListTextColumn>
        <dxwtl:TreeListCommandColumn VisibleIndex="4">
            <EditButton Visible="True">
            </EditButton>
        </dxwtl:TreeListCommandColumn>
    </Columns>
</dxwtl:ASPxTreeList>

To learn more, see Node Validation and Error Indication.