Modify DropDown List Field dynamically

Hello @SadokHanini 

To load the drop-down values dynamically, then we need to use fieldselecting event to load the values dynamically. Please find the example below. 

        protected virtual void SOOrder_UsrKNOrderReturnCodes_FieldSelecting(PXCache cache, PXFieldSelectingEventArgs e)
        {
            SOOrder row = e.Row as SOOrder;
            if (row != null)
            {
                List<string> allowedValues = new List<string>();

                foreach (KNAMICodes objAMICodes in PXSelect<KNAMICodes, Where<KNAMICodes.codeType, Equal<AMIConstants.ReturnCodes>,
                    And<KNAMICodes.isActive, Equal<True>>>>.Select(Base))
                {
                    allowedValues.Add(objAMICodes.Codecd);
                }
                e.ReturnState = PXStringState.CreateInstance(e.ReturnState, 10, true, typeof(KNAMICodes.codecd).Name, false, -1, string.Empty, allowedValues.ToArray(), allowedValues.ToArray(), false, null);
                ((PXStringState)e.ReturnState).MultiSelect = false;
            }
        }

I hope this will help you!!