Delete in Linq or Delete in Linq in Array List or Delete in Linq from Array List or Update in Linq or Update in Linq in Array List or Update in Linq in Object List

var stc_list = (from x in stc_list_
                            join y in sz on new { x.ICode, x.Clr_Code, x.SzCode } equals new { y.ICode, y.Clr_Code, y.SzCode }
                            orderby x.SzSort
                            select (new v_stock_clr_sz { ICode = x.ICode, Clr_Code = x.Clr_Code, SzCode = x.SzCode, SzQty_Pur = x.SzQty_Pur, SzQty_Sale = y.SzQty, SzQty_SaleR = x.SzQty_SaleR, SzQty_PurR = x.SzQty_PurR, SzQty_StoE = x.SzQty_StoE, SzQty_Srap = x.SzQty_Srap, stock = x.stock, SzName = x.SzName, SzSort = x.SzSort, Clr_Name = x.Clr_Name, mIcode = x.mIcode, UDI_Bar = x.UDI_Bar, Item_ID = x.Item_ID, IName = x.IName, Product_Name = x.Product_Name, Product_Name_Oth = x.Product_Name_Oth, path = x.path, photo = x.photo, photo_oth = x.photo_oth, GCode = x.GCode, SzCodeG = x.SzCodeG, GName = x.GName, SzNameG = x.SzNameG, Br_Code = x.Br_Code, Br_Name = x.Br_Name, St_Code = x.St_Code, St_Name = x.St_Name, Om_Code = x.Om_Code, Om_Name = x.Om_Name, Sg_Code = x.Sg_Code, Sg_Name = x.Sg_Name, Im_Code = x.Im_Code, Im_Name = x.Im_Name, TAX = x.TAX, Detail = x.Detail, Unit = x.Unit, Tax_Code = x.Tax_Code, HSN = x.HSN, Pur_Rate = x.Pur_Rate, Sale_Rate = x.Sale_Rate, MRP = x.MRP, Edate = x.Edate, E_ID = x.E_ID, Udate = x.Udate, U_ID = x.U_ID, U_Remark = x.U_Remark })).ToList();

        foreach (var item in stc_list)
            {
                if (get_avaiable == false)
                {
                    if (((du.Valc(item.stock) - du.Valc(item.SzQty_Sale)) < 0))
                    {
                        msg = db.msg_stock_not;
                        return (st: false, msg: msg, order_Det_List);
                    }
                }
                else
                {
                    if (du.Valc(item.SzQty_Sale) < 1 || du.Valc(item.stock) < 1)
                    {
                        sz.RemoveAll(x => x.ICode == item.ICode && x.Clr_Code == item.Clr_Code && x.SzCode == item.SzCode);
                    }
                    else
                    {
                        if ((du.Valc(item.stock) - du.Valc(item.SzQty_Sale)) < 0)
                        {
                            var udata = from x in sz
                                     where x.ICode == item.ICode && x.Clr_Code == item.Clr_Code && x.SzCode == item.SzCode
                                     select x;
                            foreach (var dd in udata)
                            {
                                dd.SzQty = du.Valc(item.stock);
                            }
                        }
                    }
                }
            }