Question

这是一个SQL查询：

SELECT Website,VendorID,Name,LinkProduct,
            Link,Logo,Image,NameExtra as Industry,
            (SELECT [Percent] FROM Web_Promotion 
            WHERE Web_Promotion.VendorID=Web_Vendor.VendorID) 
            AS PercentOff  
            FROM Web_Vendor WHERE Active='1' AND 
            (VendorID IN (Select VendorID FROM Web_Promotion 
            WHERE VendorID<>'' AND Static='True' AND [Percent] <> '0' AND 
            ((Expires>=GETDATE()) OR (Expires IS NULL))) OR 
            VendorID IN (SELECT TOP 1 SC1 FROM NavItems 
            WHERE SC1=Web_Vendor.VendorID AND Promotion<>'' 
            AND ((PromotionStart<=GETDATE() AND PromotionEnd>=GETDATE()) 
            OR (PromotionStart<=GETDATE() AND PromotionEnd IS NULL))))
            ORDER BY NameExtra,Sequence

我需要将它重写为LINQ。所以这是我的LINQ：

return await _db.Web_Vendor.
                    Where(x => !(x.WebPromotion.VendorID == string.Empty || x.WebPromotion.VendorID == null)
                    && x.WebPromotion.Static == true && x.WebPromotion.Percent != 0 &&
                    (x.WebPromotion.Expires >= DateTime.Now || x.WebPromotion.Expires == null)
                    ||
                    (_db.NavItems.Where(y => x.WebPromotion.VendorID == y.SC1
                        && !(y.Promotion == "" || y.Promotion == null)
                        && (y.PromotionStart <= DateTime.Now) && (y.PromotionEnd >= DateTime.Now || y.PromotionEnd == null))
                        .Select(g => g.SC1).Take(1).Contains(x.WebPromotion.VendorID)))
                    .Include(x => x.WebPromotion).Where(x => x.Active == true).OrderBy(x => x.NameExtra)
                    .ThenBy(x => x.Sequence).ToListAsync();

我花了大约三个，但找不到错误。原始SQL查询返回16行，但我的LINQ代码只返回13行。不幸的是，我只有一个导航属性（Web_Vendor＆lt; - ＆gt; Web_Promotion）。我认为我的查询的第二部分出现错误：

||
                        (_db.NavItems.Where(y => x.WebPromotion.VendorID == y.SC1
                            && !(y.Promotion == "" || y.Promotion == null)
                            && (y.PromotionStart <= DateTime.Now) && (y.PromotionEnd >= DateTime.Now || y.PromotionEnd == null))
                            .Select(g => g.SC1).Take(1).Contains(x.WebPromotion.VendorID)))

任何专家都可以查看我的代码并帮助我吗？正确的数据： http://prntscr.com/9a5xwu Linq数据（不正确）包含与正确相同的数据，而不是PercentOff为空的值。主要问题是LINQ在这个地方生成内连接而不是左连接：http://prntscr.com/9a6stb

Answer 1

因为你说你的linq数据在PercentOff = null时错过了，所以我专注于那个

我猜你在Linq中的“PercentOff”是Percent属性，我看到你在你的位置：“x.WebPromotion.Percent！= 0”

这是一个可以为空的值，还是将null转换为默认属性类型，即0？

不能将null转换为0，然后查询会跳过它吗？

将SQL查询重写为LINQ。找不到错误

1 个答案: