Try this
SalesOrderAdapter SO = new SalesOrderAdapter(this.oTrans);
SO.BOConnect();
SO.GetByID(SONum);
SO.SalesOrderData.OrderHed[0].Delete();
SO.Update();
Try this
SalesOrderAdapter SO = new SalesOrderAdapter(this.oTrans);
SO.BOConnect();
SO.GetByID(SONum);
SO.SalesOrderData.OrderHed[0].Delete();
SO.Update();