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  • linq中怎么实现多条件关联的左右连接

    linq左右连接最重要的是DefaultIfEmpty()这个方法和join之后的表中判断是否( temp != null)null,左右连接其实就是表的位置互换。

    1、左连接:

    from order in context.vab_OrderGoods.Where(i => i.deletef == 0 && i.order_id == orderId && i.input_type == 2)
    join goods in context.mst_Goods.Where(k => k.eigyousyo_id == _eigyousyoId)
    on order.goods_id equals goods.goods_id into ogt
    from og in ogt.DefaultIfEmpty()
    join kind in context.mst_GoodsKind.Where(l => l.deletef == 0 && l.eigyousyo_id == _eigyousyoId)
    on og.goods_kind_id equals kind.goods_kind_id into tempTable
    from temp in tempTable.DefaultIfEmpty()
    
    select new FA2_GoodsInfoModel
    {
    seq_id = order.seq_id,
    order_id = order.order_id,
    goods_id = order.goods_id,
    deletef = order.deletef,
    goods_count = order.goods_count,
    goods_name = og.goods_name,
    goods_name_kana = og.goods_name_kana,
    goods_weight = og.goods_weight,
    input_type = order.input_type,
    sub_total_goods_weight = order.sub_total_goods_weight,
    goods_kind_id = temp != null ? temp.goods_kind_id : 0,
    goods_kind_name = temp != null ? temp.goods_kind_name : string.Empty
    }

    2、右连接:

    from goods in context.mst_Goods.Where(k => k.eigyousyo_id == _eigyousyoId)
    
    join order in context.vab_OrderGoods.Where(i => i.deletef == 0 && i.order_id == orderId && i.input_type == 2)
    
    on goods.goods_id equals order.goods_id into ogt
    from og in ogt.DefaultIfEmpty()
    join kind in context.mst_GoodsKind.Where(l => l.deletef == 0 && l.eigyousyo_id == _eigyousyoId)
    on og.goods_kind_id equals kind.goods_kind_id into tempTable
    from temp in tempTable.DefaultIfEmpty()
    
     
    
    select new FA2_GoodsInfoModel
    {
    seq_id = order.seq_id,
    order_id = order.order_id,
    goods_id = order.goods_id,
    deletef = order.deletef,
    goods_count = order.goods_count,
    goods_name = og.goods_name,
    goods_name_kana = og.goods_name_kana,
    goods_weight = og.goods_weight,
    input_type = order.input_type,
    sub_total_goods_weight = order.sub_total_goods_weight,
    goods_kind_id = temp != null ? temp.goods_kind_id : 0,
    goods_kind_name = temp != null ? temp.goods_kind_name : string.Empty
    }
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  • 原文地址:https://www.cnblogs.com/dehuachenyunfei/p/7728094.html
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