Hello Suyan Dong,

You should attach to ColumnNotify event and cancel it when NotifyCode is ColumnSortingNotifyCode for the desired column:

nTreeList1.ColumnNotify += nTreeList1_ColumnNotify;
...

void nTreeList1_ColumnNotify(object sender, NTreeListColumnNotifyData data)
{
    if (data.Column == nTreeList1.Columns["Project"] && data.NotifyCode == NTreeList.ColumnSortingNotifyCode)
    {
        data.Cancel = true;
    }
}

Best Regards,
Nevron Support Team

Hi:
     When using the NTreeList control, I add NTreeListNode with subitems, I set the column's sortable to be false. But it can still sort?
could you please show me how to set it to NotSortble.
    Here is my code:
    NTreeListColumn col;
    col = new NTreeListColumn();
    col.Name = "Project";
    col.Header.Text = "Project";
    col.Sortable = false;
   
    m_List.Columns.Add(col);